CELLSEARCH CIRCULATING TUMOR CELL KIT

{0} 1 # 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY A. 510(k) Number: k073338 B. Purpose for Submission: To expand the indication for use of the CellSearch™ CTC Assay for use with metastatic prostate cancer as well as the previously cleared metastatic breast or colon cancers. C. Measurand: EpCam, Cytokeratins 8, 18 and/or 19, and CD45 D. Type of Test: A semi-automated qualitative immunomagnetic-capture, immunofluorescent detection image analysis test. E. Applicant: Veridex, LLC, A Johnson and Johnson Company F. Proprietary and Established Names: CellSearch™ Circulating Tumor Cell Kit (Epithelial) G. Regulatory Information: 1. Regulation section: 21 CFR 866.6020-Immunomagnetic Circulating Cancer Cell Selection and Enumeration System 2. Classification: Class II 3. Product code: NQI system, immunomagnetic, circulating cancer cell, enumeration 4. Panel: Immunology 82 H. Intended Use: 1. Intended use(s): The CellSearch™ Circulating Tumor Cell Kit is intended for the enumeration of circulating tumor cells (CTC) of epithelial origin (CD45-, EpCAM+, and cytokeratins 8, 18+, and/or 19+) in whole blood. 2. Indication(s) for use: The presence of CTC in the peripheral blood, as detected by the CellSearch™ Circulating Tumor Cell Kit, is associated with decreased progression free survival and decreased overall survival in patients treated for metastatic breast, colorectal or prostate* cancer. The test is to be used as an aid in the monitoring of patients with metastatic breast, colorectal or prostate cancer. Serial testing for CTC should be used in conjunction with other clinical methods for monitoring metastatic breast, colorectal and prostate cancer. Evaluation of CTC at any time during the course of disease allows assessment of patient prognosis and is predictive of progression free survival and overall survival. *Metastatic prostate cancer patients in this study were defined as having two consecutive {1} increases in the serum marker PSA above a reference level, despite standard hormonal management. These patients are commonly described as having androgen-independent, hormone-resistant, or castration-resistant prostate cancer. 3. Special conditions for use statement(s): For prescription use only. 4. Special instrument requirements: The CellTracks® AutoPrep system (k040077) and the CellTracks® Analyzer II (k050145 and k060110). The CellTracks® Analyzer II is a semi-automated fluorescence microscope intended to enumerate fluorescently labeled cells that are immunomagnetically selected and distributed over a viewing surface I. Device Description: The CellSearch™ Circulating Tumor Cell Kit consists of anti-EpCAM Ferrofluid (mouse monoclonal antibody (mAB) to EpCAM conjugated-magnetic nanoparticles in buffer with BSA and ProClin 300), staining reagent (phycoerythrin (PE)-conjugated mouse anti-cytokeratins mAB to and allophycocyanin (APC)-conjugated mouse anti-CD45 mAB in buffer with BSA and sodium azide), nucleic acid dye (4', 6-diamidino-2-phenylindole, dihydrochloride and ProClin 300), capture enhancing reagent, permeabilization reagent, cell fixative, dilution buffer, conical tubes and caps and cartridges and cartridge plugs. J. Substantial Equivalence Information: 1. Predicate device name(s): The CellSearch™ Circulating Tumor Cell Kit (for metastatic breast and colorectal cancer) 2. Predicate 510(k) number(s): k071729 3. Comparison with predicate: Similarities | Item | Device | Predicate | | --- | --- | --- | | Manufacturer | Veridex, LLC, Warren, NJ | Same | | Intended Use | The CellSearch™ Circulating Tumor Cell Kit (CellSearch) is intended for the enumeration of circulating tumor cells (CTC) of epithelial origin (CD45-, EpCAM+, and cytokeratins 8, 18+, and/or 19+) in whole blood. | Same | | Sample Type | Whole blood | Same | | Instrumentation and peripherals Used | The CellSearch system includes: CellSave Preservative Tubes, the CellTracks® AutoPrep® System, the CellTracks® Analyzer II or the CellSpotter® Analyzer, and the CellSearch™ Circulating Tumor Cell Control Kit. | Same | | Measurand | CTCs positive for EpCAM, Cytokeratins 8, 18 and/or 19 | Same | | Assay Type | Cellular | Same | {2} 3 | Item | Device | Predicate | | --- | --- | --- | | Technology | Immunomagnetic capture, enrichment and detection | Same | | Fluorescent reagents | Anti-CK-PE, DAPI, and anti-CD45-APC | Same | | Recognition of positive cells | Visual recognition through fluorescent signal | Same | | Means of measurement | Fluorescent cell counting compared to cutoff value | Same | | Cutoff for Progression/Survival | Crossing of one threshold value at any time point | Same | ## Differences | Item | New Device | Predicate | | --- | --- | --- | | Indication for Use | Metastatic prostate, colon or breast cancer | Metastatic colon cancer or breast cancer | | Clinical Performance Characteristics | Metastatic prostate cancer patients studied longitudinally | Metastatic breast and colon cancer patients studied longitudinally. | ## K. Standard/Guidance Documents Referenced: The CellSearch™ Circulating Tumor Cell kit was developed in conformance to the following standards and guidances. ISO 14971 Medical Devices- Application of Risk Management to Medical Devices Guidance for Industry and FDA Staff Class II Special Controls Guidance Document: Circulating Cancer Cell Selection and Enumeration System (May 11, 2004) Guidance for Industry and FDA Staff: Use of Symbols on Labels and in Labeling of In Vitro Diagnostic Devices Intended for Professional Use (November 30, 2004) “Guidance Document for the Submission of Tumor Associated Antigens Premarket Notifications, [510(k)], to FDA to Guide Manufacturers ## L. Test Principle: Epithelial cells are immunomagnetically labeled by targeting the Epithelial Cell Adhesion Molecule (EpCAM) antigen. Anti-EpCAM monoclonal antibodies conjugated to ferrofluid particles are colloidal and, when mixed with a sample containing the target epithelial cells, bind to the EpCAM antigen associated with the epithelial cells. After immunomagnetic selection of epithelial cells from 7.5 mL of blood, fluorescent reagents are added at this time to discriminate between the immunomagnetically selected cells. Anti-Cytokeratin – Phycoerythrin (CK-PE) stains the intracellular cytoskeleton cytokeratin proteins expressed in cells of epithelial origin, anti-CD45-Allophycocyan (CD45-APC) stains leukocytes and DAPI {3} stains DNA present in the cell nucleus. The processed reagent/sample mixture is dispensed by the CellTracks® AutoPrep System into a cartridge that is inserted into a MagNest® cell presentation device. The strong magnetic field of the MagNest® device causes the magnetically-labeled target cells to move to the surface of the cartridge. The cartridge is then placed on the CellTracks® Analyzer II for data acquisition and analysis. The CellTracks Analyzer II scans the entire surface of the cartridge with a series of fluorescence filters that are defined for a given assay and acquires images of PE, APC and DAPI fluorescence staining of the entire viewing surface. After data acquisition is completed, the images are analyzed for any event where cytokeratin-PE and DAPI are within a specified space in the cartridge, i.e. indicating the possible presence of a cell with a nucleus that expresses cytokeratin. Images from each fluorescent color as well as a composite image of the cytokeratin staining (green) and the nuclear staining (purple) are presented to the user in a gallery for final cell classification. A cell is classified as a tumor cell when it its EpCAM+ (i.e., it is captured), CK+, DAPI+ and CD45-. A check mark placed by the operator next to the composite images classifies the event as a Circulating Tumor Cell (CTC) and the software tallies all the checked boxes to obtain the CTC count. ## M. Performance Characteristics (if/when applicable): 1. Analytical performance was presented originally in k031588: a. Precision/Reproducibility: i. System Reproducibility with CellSearch™ Circulating Tumor Cell Control Three separate CellSearch™ Circulating Tumor Cell Control samples were prepared and processed each day for over 30 days, per the long run method of NCCLS guideline EP5-A². Each single-use sample bottle contains a low and a high concentration of cells from a fixed cell line that have been pre-stained with two different fluorochromes. Summary statistics for the high and low control cells is presented below. Table 1. Summary of Precision Analyses | | Low | High | | --- | --- | --- | | N | 99 | 99 | | Mean cell count | 48 | 969 | | Total Precision Standard Deviation (S_T) % CV | 18% | 5% | ii. System Reproducibility with Patient Samples A total of 163 duplicate blood samples were collected from 47 metastatic breast cancer patients over the course of the clinical study. These samples were processed at multiple sites to determine the reproducibility of CTC measurements. The regression equation for the comparison of these 163 duplicate samples was $Y = 0.98x + 0.67$, $R^2 = 0.99$. Figure 1 shows a scatter plot of the duplicate CTC results in blood from MBC patients plotted on a logarithmic scale, with the threshold of 5 CTC indicated by the dashed {4} lines.  Figure 1. Reproducibility of CTC Counts in Duplicate MBC Samples $(n = 163)$ with Average of $&lt; 5$ or $\geq 5$ CTC per $7.5\mathrm{mL}$ of blood. Figure 2 Note: There may be more than one point superimposed over another. For example, on this plot, there are 50 instances $(31\%)$ where both tubes had 0 CTC, 18 instances $(11\%)$ where Tube 1 had 0 CTC and Tube 2 had 1 CTC, and another 18 instances $(11\%)$ where Tube 1 had 1 CTC and Tube 2 had 0 CTC. # Metastatic Colorectal Cancer (MCRC) A total 1,627 duplicate blood samples were collected from 430 MCRC patients over the course of the clinical study. These samples were processed at multiple sites to determine the reproducibility of CTC measurements. The regression equation for the comparison of these 1,627 duplicate samples was $\mathrm{Y} = 0.98\mathrm{x} + 0.18$ , $\mathrm{R}^2 = 0.96$ . Figure 2 shows a scatter plot of the duplicate CTC results in blood from MCRC patients plotted on a logarithmic scale, with the threshold of 3 CTC indicated by the dashed lines. Figure 2. Reproducibility of CTC Counts in Duplicate MCRC Samples (n=1627) with Average of $&lt; 3$ or $\geq 3$ CTC per $7.5\mathrm{mL}$ of blood. {5}  Figure 3 Note: There may be more than one point superimposed over another. For example, on this plot, there are 975 instances (60%) where both tubes had 0 CTC, 116 instances (7%) where Tube 1 had 0 CTC and Tube 2 had 1 CTC, and another 109 instances (7%) where Tube 1 had 1 CTC and Tube 2 had 0 CTC. The tube-to-tube variation of CTC counts in blood samples from metastatic breast and colorectal cancer patients is shown in Figures 1 &amp; 2. The distribution of infrequent events (such as tumor cells) within a given volume is random and independent of cell or disease type. This is best characterized by the Poisson distribution – a mathematical method employed for modeling systems where the probability of an event occurring is very low but the number of opportunities for such an event to occur is large. For tubes with very few prostatic CTC it is reasonable to expect variation in results similar to what is depicted in Figures 1 &amp; 2. Because the two previous studies in MBC and MCRC patients showed almost identical results, a tube-to-tube comparison of CTC counts in blood samples from metastatic prostate cancer patients was not performed during the CellSearch™ CTC prostate clinical trial. However, results of an independent study using CellSearch™ technology conducted at the Memorial Sloan-Kettering Cancer Center demonstrated no systematic site-to-site or tube-to-tube variation in CTC counts across a range of 0 to 1192 CTC per tube in patients with metastatic prostate cancer # Accuracy/Recovery: Blood samples from a single healthy donor were pooled and five of six 7.5 {6} mL aliquots were spiked with 5, 20, 81, 325 and 1300 cultured breast cancer cells (SK-Br-3). The sixth tube was unspiked pooled blood and served as a zero point. These samples were processed on the CellTracks® AutoPrep System with the CellSearch™ Circulating Tumor Cell Kit and CTC counts were determined on the CellTracks® Analyzer II. The experiment was repeated for four additional donors. The observed cell counts were plotted against the results of the expected cell count. The results are summarized in Table 2. Table 2. Percent Detection Estimates. | Expected Tumor Cell Count | Mean Observed Tumor Cell Count | Range of Percent Recovery | | --- | --- | --- | | 1300 | 1215 | 91 to 95% | | 325 | 308 | 82 to 101% | | 81 | 85 | 80 to 136% | | 20 | 22 | 95 to 140% | | 5 | 7 | 120 to 200% | To determine the overall, or least squares fit, for the comparison of the observed and expected cell counts across all the data, linear regression analysis was performed. The regression equation for these 30 samples was $y = 0.93x + 3.87$, $R^2 = 0.999$. The results of this study indicate that on average over the tested CTC range the recovery, as derived from regression analysis, is 93%. Given the linear response of the tumor cell counts, one would expect the slope of the observed versus expected plot to be 1.0. However, the slope was 0.93. This is because the CellTracks® AutoPrep System with CellSearch™ CTC Kit involves the capture and fluorescent labeling of cells followed by their detection and enumeration by the CellTracks® Analyzer II. The loss of cells could therefore be attributed to one of the following possibilities; 1) the recovery of only 93% of the tumor cells spiked into 7.5mL of blood by the CellTracks® AutoPrep System, 2) the detection of only 93% of the tumor cells present in the sample chamber by the CellTracks® Analyzer II or 3) a combination of both of these sources of error. b. Linearity/assay reportable range: Another way to examine the previous data is to analyze it as a dilution series to evaluate test linearity. The confounding variable of percent recovery was removed by using the observed value of the original sample divided by the dilution factors to determine the expected values for the dilution series for each patient sample. Regression of all of these numbers of observed tumor cells versus the numbers of expected tumor cells yielded a slope of 1.007, an intercept of 3.0, an $r^2 = 0.99$ and $r = 0.995$. Therefore, once the percent recovery (cell loss) was factored out of the CTC values of each of the original {7} samples, this analysis of the data demonstrated that the detection of CTC was linear over the reportable range of 0 to 1238 tumor cells. c. Traceability, Stability, Expected values (controls, calibrators, or methods): No recognized reference material or method. d. Detection limit: One CTC per 7.5 mL can be detected by the CellTracks® Analyzer II resulting in a limit of detection of 1 CTC in a cartridge. Linear regression shows that on average, 93% of CTC present in a 7.5 mL blood sample are recovered using the CellTracks® AutoPrep System (see Recovery section). The loss of approximately 7% of the CTC in the sample is not sufficient to reduce the limit of detection of 1 CTC. d. Analytical specificity Interfering Substances: Interference studies were not performed for prostate cancer cells. In the submission for metastatic breast cancer, SK-BR-3 cells spiked into blood samples were exposed to potential interfering substances and compared to untreated controls. Toxic levels (5 times therapeutic index) of the following cancer drugs, over-the-counter drugs, and other exogenous substances were tested: cyclophosphamide, Mitomycin C®, Procrit®, biotin, 5-fluorouracil, methotrexate, tamoxifen citrate, paclitaxel, Arimidex®, acetaminophen, acetylsalicylic acid, caffeine, dextromethorphan, Aredia®, Herceptin®, and ibuprofen. No significant differences in SK-BR-3 cell numbers were detected, indicating that these substances do not interfere with the CellSearch™ kit. Samples spiked with toxic levels of doxorubicin resulted in aberrant staining of leukocytes as cytokeratin and CD45 dual positive cells, due to the doxorubicin being a fluorescent compound that is incorporated into nucleated cells. If seen, the staining pattern of all cells being CD45 positive and cytokeratin positive is obvious and easily identified by the operator as a known interference staining profile. If blood is drawn after the recommended 7-day washout period, following doxorubicin infusion, this interference is unlikely to be observed in clinical practice given controlled therapeutic levels and rapid drug clearance. Potential interference from lipemia was studied by adding Intralipid to samples to a concentration of 2.6%, which corresponds to greater than 1000 mg/dL triglyceride. Samples were lysed to simulate total hemolysis. Bilirubin at 7.4 mg/dL, HAMA type 1/HAMA type 2 and hematocrit from 18-60% were studied. Lipemia, hemolysis, icterus and a broad range of hematocrit values do not interfere with the CellSearch™ test. HAMA 1 and HAMA 2 also do not interfere, indicating that individuals receiving mouse Ig by parenteral routes can be tested successfully with the CellSearch™ test. f. Assay cut-off: Results are reported as the number of CTC/7.5 mL of blood. A CTC count of 5 or more per 7.5 mL of blood is predictive of shorter progression free survival and overall survival for metastatic prostate cancer. 8 {8} # 2. Comparison studies: a. Method comparison with predicate device: Direct comparison to the predicate device is not feasible since the patient population used by the two tests is different (metastatic breast cancer vs. metastatic colon cancer) rather, clinical studies are necessary to establish the new indication for use. These were performed by the sponsor. b. Matrix comparison: Since there is only one matrix for this test, i.e. whole blood, no matrix comparison studies were performed. # 3. Clinical studies: a. Clinical Sensitivity: Not applicable b. Clinical specificity: Not applicable c. Other clinical supportive data (when a. and b. are not applicable): # Clinical Studies to Support Prognostic Use of Veridex CTC Test with Metastatic Prostate Cancer (MPC) Patients A multi-center prospective, clinical trial was conducted to determine whether the number of CTC predicted disease progression and survival. Metastatic prostate cancer patients in this study were defined as having two consecutive increases in the serum marker prostate-specific antigen (PSA) above a reference level, despite standard hormonal management. These patients are commonly described as having androgen-independent, hormone-resistant, or castration-resistant prostate cancer. A total of 231 metastatic prostate cancer patients with evidence of (PSA) progression despite standard hormonal therapy and starting a new line or type of chemotherapy were enrolled. Clinical data were analyzed on an intent-to-treat basis. Patient demographic information is presented in Table 3. Table 3: MPC Patient Demographics | Category | Mean ± Std. Deviation (Median) | Number of Subjects | | --- | --- | --- | | Age at Baseline (in years) | 70 ± 9 (70) | 231 | | Pre-Therapy: | | | | PSA (ng/mL) | 547 ± 1616 (144) | 231 | | Hemoglobin (g/dL) | 12.3 ± 1.6 (12.4) | 221 | | Alkaline Phosphatase(AlkPhos) (IU/mL) | 235 ± 271 (144) | 223 | | Lactate dehydrogenase (LDH) (IU/mL) | 293 ± 228 (224) | 219 | | Albumin (g/dL) | 3.9 ± 2.6 (3.8) | 214 | | | Description of Categories | Number of Subjects (% of total) | | Race | White | 209 (90%) | | | Black | 17 (7%) | | | Other | 5 (3%) | | Baseline ECOG Score | 0 | 101 (44%) | | | 1 | 100 (43%) | | | 2 | 21 (9%) | | | Unknown | 9 (4%) | | Gleason Score | ≥5 | 18 (8%) | | | 6 | 28 (12%) | | | 7 | 63 (27%) | | | 8 | 45 (20%) | {9} | | ≥9 Unknown | 54 (23%) 23 (10%) | | --- | --- | --- | | Stage at Primary Diagnosis | 1 2 3 4 Unknown | 14 (6%) 30 (13%) 58 (25%) 19 (8%) 110 (48%) | | Line of Therapy | 1st 2nd ≥3rd | 154 (67%) 38 (16%) 39 (17%) | | Taxotere in Current Therapy Line | No Yes Unknown | 67 (29%) 162 (70%) 2 (1%) | | Bone Metastasis | Negative Positive Unknown | 20 (8%) 207 (90%) 4 (2%) | | Measurable Disease | No Yes Unknown | 142 (62%) 88 (38%) 1 (0%) | | Visceral Metastasis | No Yes Unknown | 141 (61%) 89 (39%) 1 (0%) | Baseline CTC count was determined prior to initiation of a new line of chemotherapy. The following timeframes were chosen for evaluation: baseline (prior to the initiation of therapy), 2-5 weeks (14 - 41 days from baseline), 6-8 weeks (42 - 62 days from baseline), 9-12 weeks (63 - 90 days from baseline), and 13-20 weeks (91 - 146 days from baseline) after the initiation of therapy. If more than one blood draw fell within the designated timeframes, the blood draw furthest from the baseline blood draw was used as the result for each timeframe. ## CTC frequencies All 231 evaluable MPC patients had a baseline blood draw. Two hundred and twenty-one (221) of these MPC patients had one or more follow-up blood draws after the initiation of therapy. Of the ten MPC patients with only a baseline blood draw, three died before a follow-up blood draw could be obtained, one progressed and was sent to hospice, one stopped their chemotherapy due to a broken hip, one patient moved, three refused any further blood draws, and one withdrew their consent for the study. There were a total of 214, 171, 158, and 149 MPC patients with follow-up blood draws 2-5 weeks, 6-8 weeks, 9-12 weeks, and 13-20 weeks after the initiation of therapy, respectively. In metastatic prostate cancer, disease progression is primarily determined using changes in PSA. For this study, disease progression was determined by the sites using PSA, imaging, and/or clinical signs and symptoms. For the baseline analyses, progression free survival (PFS) was determined from the time of the baseline blood draw to the determination of progression or death, and overall survival (OS) was determined from the time of the baseline blood draw to the date of death or the date of last contact with the patient. For the follow-up analyses, PFS was determined from the time of the follow-up blood draw to diagnosis of progression or death, and OS was determined from the time of the follow-up blood draw to the date of death or the date of last contact with the patient. {10} Patients with progression prior to the date of the blood draw being evaluated were excluded from the PFS analyses of that time point and all subsequent follow-up blood draws. Patients with no additional survival follow-up beyond the date of the blood draw being evaluated were excluded from the PFS &amp; OS analyses of that time point. Table 4 shows the numbers of patients at each time point excluded from the PFS or PFS &amp; OS analyses and the reasons for their exclusion. Table 4: Exclusions from PFS and OS Analyses in MPC Patients | Blood Draw Timing | MPC Patients Not Evaluable: | | | | | Total # of MPC Patients Evaluable | | | --- | --- | --- | --- | --- | --- | --- | --- | | | PFS & OS | | | | PFS Only | | | | | Blood Not Drawn | Blood Drawn 1-7 days after therapy administration | No Follow-up Beyond Date of Blood Draw | No or Non-Evaluable CTC Results | Blood drawn after date of disease progression | PFS | OS | | Baseline | 0 | 6 | 0 | 6 | 0 | 219 | 219 | | 2-5 Weeks | 17 | 0 | 0 | 11 | 4 | 199 | 203 | | 6-8 Weeks | 60 | 0 | 0 | 8 | 22 | 141 | 163 | | 9-12 Weeks | 73 | 1 | 0 | 8 | 15 | 134 | 149 | | 13-20 Weeks | 82 | 0 | 1 | 5 | 27 | 116 | 143 | The CTC results obtained from the baseline and follow-up blood draws at 2-5 weeks, 6-8 weeks, 9-12 weeks, and 13-20 weeks after the initiation of therapy were classified as being favorable (&lt;5 CTC) or unfavorable (≥5 CTC). The PSA, Alkaline Phosphatase, and LDH levels summarized in the demographics table and used in the analyses were all measured at a central laboratory in serum samples collected at the same time as the blood samples used for CTC evaluation. The hemoglobin and albumin levels summarized in the tables and used in the analyses were values provided by the sites and verified from the patient's medical records that were determined within ± 30 days of the baseline CTC evaluation. ## Progression Free Survival (PFS) Analysis of MPC Patients ## PFS Using Baseline CTC Results Two hundred nineteen (219) of the 231 evaluable patients had a baseline CTC result available. For Kaplan-Meier analysis, patients were segmented into two groups based upon their CTC count at baseline: - The Favorable group (N=94), represented in green, consisted of patients with &lt;5 CTC. - The Unfavorable group (N=125), represented in red, consisted of patients with ≥5 CTC. Median PFS was longer in the Favorable group compared to the Unfavorable group (5.8 vs. 4.2 months, respectively.) These results are illustrated in Figure 3 or Table 5. {11}  Figure 3: PFS of MPC Patients with $&lt; 5$ or $\geq 5$ CTC at Baseline (N = 219). # PFS Using Follow-up CTC Results For Kaplan-Meier analysis, MPC patients were segmented into two groups based upon their CTC count at each of the various follow-up blood draws. Both patient groups at each of the different follow-up blood draws after initiation of therapy for PFS are illustrated in Figure 4. This figure illustrates the ability of CTC in MPC patients with $&lt;5$ and $\geq 5$ CTC to predict time to clinical progression or death at 2-5 weeks (n=199), 6-8 weeks (n=141), 9-12 weeks (n=134) and 13-20 weeks (n=116) after the initiation of therapy. - The Favorable group represented in olive green, blue, purple, and cyan consisted of patients with $&lt; 5$ CTC at 2-5, 6-8, 9-12, and 13-20 weeks after the initiation of therapy, respectively. - The Unfavorable group, represented in brown, black, grey, and orange consisted of patients with $\geq 5$ CTC at 2-5, 6-8, 9-12, and 13-20 weeks after the initiation of therapy, respectively. {12}  Figure 4: PFS of MPC Patients with $&lt; 5$ or $\geq 5$ CTC at different times of Follow-Up Table 5 summarizes the results of the PFS analysis using the CTC levels and a threshold of $\geq 5$ CTC/7.5mL at each of the different blood draw time points. Table 5: Progression Free Survival (PFS) for MPC patients with $&lt; 5$ or $\geq 5$ CTC at different time points | Sampling Time After Tx Initiation | N | ≥5 CTC | Median PFS in Months (95% CI) | | Log-rank p-value | | --- | --- | --- | --- | --- | --- | | | | | <5 CTC | ≥5 CTC | | | Baseline | 219 | 125 (57%) | 5.8 (5.0 – 7.9) | 4.2 (3.1 – 4.9) | 0.0008 | | 2-5 Weeks | 199 | 77 (39%) | 6.5 (4.9 – 7.4) | 2.1 (1.4 – 3.3) | <0.0001 | | 6-8 Weeks | 141 | 38 (27%) | 5.9 (4.2 – 7.0) | 1.9 (1.3 – 2.7) | <0.0001 | | 9-12 Weeks | 134 | 39 (24%) | 4.9 (3.8 – 6.2) | 1.6 (0.9 – 2.6) | <0.0001 | | 13-20 Weeks | 116 | 27 (23%) | 4.1 (3.3 – 5.8) | 1.2 (0.5 – 1.5) | <0.0001 | As illustrated in Figure 4 and Table 5, MPC patients with elevated CTC ( $\geq$ 5 CTC/7.5mL whole blood) at any of the time points had a much higher likelihood of rapid progression than did those with $&lt; 5$ CTC. Table 5 column 4 shows the median PFS times for those patients with $&lt; 5$ CTC ranged from 4.1 to 6.5 months and were substantially longer than the median PFS times for those patients with $\geq 5$ CTC, which ranged from 1.2 to 4.2 months (column 5). {13} 14 # Reduction or Increase in CTC Predicts Improved or Decreased PFS Elapsed PFS times were calculated from the baseline blood draw. For the Kaplan-Meier analysis shown in Figure 5, MPC patients were segmented into four groups based upon their CTC counts at baseline, 2-5 weeks, 6-8 weeks, 9-12 weeks, and 13-20 weeks after the initiation of therapy: - Group 1 (green curve), 88 (38%) patients with &lt;5 CTC at all time points. Five (6%) of these patients only had a baseline blood draw while seven (8%) had a single blood draw between their first and last blood draw that had ≥5 CTC; - Group 2 (blue curve), 45 (20%) patients with ≥5 CTC prior to the initiation of therapy but who had decreased to &lt;5 CTC at the time of their last blood draw; - Group 3 (orange curve), 26 (11%) patients with &lt;5 CTC at an early draw (baseline, 2-5 weeks, and/or 6-8 weeks) but who increased to ≥5 CTC at the time of their last blood draw; - Group 4 (red curve), 71 (31%) patients with ≥5 CTC at all draw time points. Eight (11%) of these patients had only a baseline blood draw and two (3%) had a single blood draw between their first and last blood draw that had &lt;5 CTC. Figure 5 shows that MPC patients with ≥5 CTC at all time points (Group 4) had the shortest median PFS, which was significantly different compared to the median PFS of Group 3, Group 2 and Group 1. The difference in the median PFS between those patients who showed a CTC reduction after the initiation of therapy (Group 2) was significantly longer compared to those patients who showed a CTC increase (Group 3). Overall Survival (OS) Analysis of MPC Patients Figure 5: A Reduction in CTC Below 5 After the Initiation of Therapy Predicts Longer PFS in MPC Patients {14}  # OS Analysis Using Baseline CTC Results Death occurred in 119 (52%) of the 231 MPC patients, with a mean follow-up time for the 112 (48%) patients still alive of $16.1 \pm 4.9$ months (median = 16.5 months, range = 1.9 to 25.7 months). At the time of these analyses, 28 (30%) of 94 patients from the Favorable group (&lt;5 CTC at baseline) compared to 83 (66%) of 125 from the Unfavorable group ( $\geq 5$ CTC at baseline) had died. For Kaplan-Meier analysis, the 219 of the 231 evaluable patients that had baseline results were segmented into two groups based upon their CTC count at baseline: - The Favorable group $(N = 94)$ , represented in green, consisted of patients with $&lt; 5$ CTC. - The Unfavorable group $(N = 125)$ , represented in red, consisted of patients with $\geq 5$ CTC. Median OS was significantly longer in the Favorable group compared to the Unfavorable group (21.7 vs. 11.5 months, respectively). These results are illustrated in Figure 6. {15}  Figure 6: OS of MPC Patients with $&lt;5$ or $\geq 5$ CTC at Baseline (N = 219). # OS Using Follow-up CTC Results The Kaplan-Meier analyses of both MPC patient groups at each of the different follow-up blood draw times after initiation of therapy are illustrated in Figure 7. This figure illustrates the ability of CTC in MPC patients with $&lt;5$ and $\geq 5$ CTC 2-5 weeks (n=203), 6-8 weeks (n=163), 9-12 weeks (n=149) and 13-20 weeks (n=143) after the initiation of therapy to predict time to death. OS times were calculated from the time of each blood draw. - The Favorable group, represented in olive green, blue, purple, and cyan, consisted of patients with $&lt; 5$ CTC, - The Unfavorable group, represented in brown, black, grey, and orange, consisted of patients with $\geq 5$ CTC. {16}  Figure 7: OS of MPC Patients with $&lt; 5$ or $\geq 5$ CTC at different times of Follow-Up. Table 6 summarizes the results of the OS analysis using the CTC levels and a threshold of $\geq 5$ CTC/7.5mL at each of the different blood draw time points. Table 6: Overall Survival (OS) for MPC patients with $&lt; 5$ or $\geq 5$ CTC at different time points | Sampling Time After Tx Initiation | N | ≥5 CTC | Median OS in Months (95% CI) | | Log-rank p-value | | --- | --- | --- | --- | --- | --- | | | | | <5 CTCs | ≥5 CTCs | | | Baseline | 219 | 125 (57%) | 21.7 (21.3 - NR) | 11.5 (9.3 - 13.7) | <0.0001 | | 2-5 Weeks | 203 | 80 (39%) | 20.7 (20.5 - NR) | 9.5 (5.8 - 10.7) | <0.0001 | | 6-8 Weeks | 163 | 53 (33%) | 19.9 (17.9 - NR) | 8.5 (5.0 - 10.2) | <0.0001 | | 9-12 Weeks | 149 | 49 (33%) | 19.6 (18.5 - NR) | 7.6 (6.2 - 8.6) | <0.0001 | | 13-20 Weeks | 143 | 44 (31%) | 19.8 (17.1 - NR) | 6.7 (4.9 - 7.6) | <0.0001 | As illustrated in Figure 7 and Table 6 in columns 4 &amp; 5, MPC patients with $\geq 5$ CTC at any of the time points had a much higher likelihood of dying sooner than did those with $&lt; 5$ CTC. The median OS times for those patients with $&lt; 5$ CTC ranged from 19.6 to 21.7 {17} months and were substantially longer than the median OS times for those patients with $\geq 5$ CTC, which ranged from 6.7 to 11.5 months. ## Reduction or Increase of CTC Predicts Improved or Decreased OS Elapsed OS times were calculated from the baseline blood draw. For Kaplan-Meier analysis (Figure 8), patients were segmented into four groups based upon their CTC counts at baseline, 2-5 weeks, 6-8 weeks, 9-12 weeks, and 13-20 weeks after the initiation of therapy: - Group 1 (green curve), 88 (38%) patients with &lt;5 CTC at all time points. Five (6%) of these patients had only a baseline blood draw while seven (8%) had a single blood draw between their first and last blood draw that had ≥5 CTC; - Group 2 (blue curve), 45 (20%) patients with ≥5 CTC prior to the initiation of therapy but who had decreased to &lt;5 CTC at the time of their last blood draw; - Group 3 (orange curve), 26 (11%) patients with &lt;5 CTC at an early draw but who increased to ≥5 CTC at the time of their last blood draw; - Group 4 (red curve), 71 (31%) patients with ≥5 CTC at all draw time points. Eight (11%) of these patients had only a baseline blood draw and two (3%) had a single blood draw between their first and last blood draw that had &lt;5 CTC. Figure 8: A Reduction in CTC Below 5 After the Initiation of Therapy Predicts Longer OS whereas an Increase in CTC Count to 5 or above Predicts Shorter OS in MPC Patients {18}  Figure 8 shows that those patients with $\geq 5$ CTC at any point after the initiation of therapy had a much higher likelihood of dying sooner. Patients with $\geq 5$ CTC at all time points (Group 4) had the shortest median OS, which was significantly different compared to the median OS of Group 2, and Group 1 but not Group 3. Patients with $&lt; 5$ CTC at all time points (Group 1) had the longest median OS, which was significantly different compared to the median OS of Group 4 and Group 3, but not Group 2. Figure 8 also demonstrated that patients who showed a decrease in CTC (Group 2) improve their survival chances and had a median OS similar to those patients with favorable CTC at all draws (Group 1). The figure also shows that unfavorable CTC levels after the initiation of therapy significantly decreased overall survival (Group 3 and Group 4). # Univariate Cox Regression Analysis in MPC Patients Univariate Cox proportional hazards regression analysis was used to evaluate the association of the following pre-treatment parameters with PFS and OS: stage of disease at diagnosis (1-4), patient age ( $\geq 70$ or $&lt; 70$ years), ECOG status before initiation of a new line of therapy (0-2), Gleason score (2-10), hemoglobin level within $\pm 30$ days of baseline draw (g/dL, continuous), albumin level within $\pm 30$ days of baseline draw (g/dL, continuous), testosterone level at the time of the baseline draw (ng/mL, continuous), LDH level at the time of the baseline draw (IU/mL, continuous), alkaline phosphatase {19} level at the time of the baseline draw (IU/mL, continuous), PSA level at the time of the baseline draw (ng/mL, continuous), pre-treatment PSA doubling time (months, continuous), pre-treatment PSA velocity (ng/mL/month, continuous), line of therapy $(1^{\mathrm{st}}$ , $2^{\mathrm{nd}}$ , $3^{\mathrm{rd}}$ , $4^{\mathrm{th}}$ , $5^{\mathrm{th}}$ , or $6^{\mathrm{th}})$ , type of therapy (taxotere included or not), presence of measurable disease (yes or no), presence of bone metastasis (yes or no), presence of visceral metastasis (yes or no), and baseline CTC level ( $\geq 5$ CTC/7.5mL or $&lt; 5$ CTC/7.5mL) and follow up CTC counts at 2-5, 6-8, 9-12 and 13-20 weeks. For these analyses, the elapsed times for both PFS and OS were calculated from the time of the baseline blood draw. The Cox regression results (i.e. the hazards ratio and associated $95\%$ confidence interval, chi-square value, and associated p-values) for the ability of the parameters to independently predict PFS and OS are provided in Table 7 as well as the number of patients in each evaluation. Table 7: Univariate Cox Regression Analysis in MPC Patients | Parameter | Categories | | # of MPC Patients | PFS Risk from Baseline | | OS Risk From Baseline | | | --- | --- | --- | --- | --- | --- | --- | --- | | | Positive | Negative | | HR | p-value1 | HR | p-value1 | | Stage at Primary Diagnosis | 4 vs. 3 vs. 2 vs. 1 | | 121 | 0.88 | 0.206 | 0.83 | 0.174 | | Age at Baseline Blood Draw | ≥70 | <70 | 231 | 0.96 | 0.764 | 1.28 | 0.178 | | ECOG Status at Study Entry | 2 vs. 1 vs. 0 | | 222 | 1.34 | 0.011 | 2.36 | <0.001 | | Gleason Score | 10 to 2 | | 208 | 1.01 | 0.919 | 1.02 | 0.717 | | Pre-treatment PSA Doubling Time (Months) | Continuous | | 230 | 0.97 | 0.542 | 0.97 | 0.664 | | Pre-treatment PSA Velocity (ng/mL/Month) | Continuous | | 230 | 1.00 | 0.200 | 1.00 | 0.544 | | Baseline Hemoglobin (g/dL) | Continuous | | 221 | 0.87 | 0.002 | 0.71 | <0.001 | | Baseline Albumin (g/dL) | Continuous | | 214 | 0.99 | 0.748 | 1.02 | 0.557 | | Baseline Testosterone (ng/mL)1 | Continuous | | 223 | 1.07 | 0.900 | 2.71 | 0.060 | | Baseline LDH (IU/mL)1 | Continuous | | 219 | 1.001 | <0.001 | 1.002 | <0.001 | | Baseline Alkaline Phosphatase (IU/mL)1 | Continuous | | 223 | 1.00 | 0.158 | 1.0008 | 0.001 | | Line of Therapy | Continuous (1 - 6) | | 231 | 1.23 | 0.003 | 1.28 | 0.003 | | Type of Therapy (Taxotere: Yes/No) | Yes | No | 229 | 0.57 | <0.001 | 0.59 | 0.006 | | Measurable Disease? | Yes | No | 230 | 1.00 | 0.993 | 1.28 | 0.181 | | Bone Metastasis? | Yes | No | 227 | 1.02 | 0.933 | 2.22 | 0.057 | | Visceral Metastasis? | Yes | No | 230 | 1.01 | 0.918 | 1.26 | 0.216 | | Baseline PSA (ng/mL)1 | Continuous | | 231 | 1.00 | 0.746 | 1.00 | 0.907 | | 2 - 5 Week PSA (ng/mL)1 | Continuous | | 207 | 1.00 | 0.819 | 1.00 | 0.794 | | 6 - 8 Week PSA (ng/mL)1 | Continuous | | 167 | 1.00 | 0.426 | 1.00 | 0.654 | | 9 - 12 Week PSA (ng/mL)1 | Continuous | | 155 | 1.00 | 0.684 | 1.00 | 0.324 | | 13 - 20 Week PSA (ng/mL)1 | Continuous | | 143 | 1.00 | 0.639 | 1.00 | 0.205 | | 2 - 5 Week PSA Reduction from BL (%)1 | <30% | ≥30% | 207 | 1.56 | 0.006 | 1.24 | 0.318 | | 6 - 8 Week PSA Reduction from BL (%)1 | <30% | ≥30% | 167 | 2.21 | <0.001 | 2.27 | 0.001 | {20} | Parameter | Categories | | # of MPC Patients | PFS Risk from Baseline | | OS Risk from Baseline | | | --- | --- | --- | --- | --- | --- | --- | --- | | | Positive | Negative | | HR | p-value2 | HR | p-value2 | | 9 - 12 Week PSA Reduction from BL (%)1 | <30% | ≥30% | 155 | 2.76 | <0.001 | 2.30 | <0.001 | | 13 - 20 Week PSA Reduction from BL (%)1 | <30% | ≥30% | 143 | 2.69 | <0.001 | 3.19 | <0.001 | | Baseline CTC Number | ≥5 | <5 | 219 | 1.62 | 0.001 | 3.33 | <0.001 | | 2 - 5 Week CTC Number | ≥5 | <5 | 203 | 2.34 | <0.001 | 4.46 | <0.001 | | 6 - 8 Week CTC Number | ≥5 | <5 | 163 | 3.29 | <0.001 | 3.66 | <0.001 | | 9 - 12 Week CTC Number | ≥5 | <5 | 149 | 3.23 | <0.001 | 5.82 | <0.001 | | 13 - 20 Week CTC Number | ≥5 | <5 | 144 | 4.82 | <0.001 | 7.18 | <0.001 | 1 Determined from Serum Drawn on the Same Date as the Blood Drawn for CTC ${}^{2}$ p-value from Wald test of Z statistic 3 p-value from chi-squared test # Multivariate Cox Regression Analysis in MPC Patients Multivariate Cox regression analyses were conducted to evaluate the independent predictive power of CTC count by adjusting for the effects of the known important clinical factors that are statistically significant in the univariate analyses. CTC were found to be strongest predictors at most time points of PFS and OS (Table 8). Table 8: Multivariate Cox Regression Analysis in MPC Patients | Parameter | # of Patients | PFS Risk from Baseline | | OS Risk from Baseline | | | --- | --- | --- | --- | --- | --- | | | | HR | p-value2 | HR | p-value2 | | Baseline CTC (<5 vs. ≥5) | 188 | 1.14 | 0.455 | 1.92 | 0.009 | | Baseline ECOG Status (0 vs. 1 vs. 2) | | 1.00 | 0.982 | 1.46 | 0.032 | | Baseline Hemoglobin (g/dL)3 | | 0.88 | 0.027 | 0.81 | 0.007 | | Baseline LDH (IU/mL)1,3 | | 1.0007 | 0.018 | 1.002 | <0.001 | | Baseline Alkaline Phosphatase (IU/mL)1,3 | | --- | --- | 1.00 | 0.410 | | Line of Therapy (1stthrough 6th) | | 1.14 | 0.145 | 1.07 | 0.547 | | Type of Therapy (Taxotere: Yes/No) | | 0.63 | 0.009 | 0.70 | 0.139 | | 2 - 5 Week CTC (<5 vs. ≥5) | 173 | 1.48 | 0.041 | 2.91 | <0.001 | | 2 - 5 Week PSA Reduction from Baseline (≥30% vs. <30%)1 | | 1.40 | 0.077 | 1.13 | 0.637 | | Baseline ECOG Status (0 vs. 1 vs. 2) | | 0.97 | 0.836 | 1.46 | 0.054 | | Baseline Hemoglobin (g/dL)3 | | 0.93 | 0.246 | 0.89 | 0.141 | | Baseline LDH (IU/mL)1,3 | | 1.002 | 0.002 | 1.003 | <0.001 | | Baseline Alkaline Phosphatase (IU/mL)1,3 | | --- | --- | 1.00 | 0.622 | | Line of Therapy (1stthrough 6th) | | 1.11 | 0.274 | 1.11 | 0.399 | | Type of Therapy (Taxotere: Yes/No) | | 0.75 | 0.133 | 0.80 | 0.397 | | 6 - 8 Week CTC (<5 vs. ≥5) | 139 | 2.14 | <0.001 | 2.13 | 0.009 | | 6 - 8 Week PSA Reduction from Baseline (≥30% vs. <30%)1 | | 1.88 | 0.002 | 2.38 | 0.007 | | Baseline ECOG Status (0 vs. 1 vs. 2) | | 1.04 | 0.810 | 1.52 | 0.088 | | Baseline Hemoglobin (g/dL)3 | | 0.97 | 0.695 | 0.79 | 0.013 | {21} | Parameter | # of Patients | PFS Risk from Baseline | | OS Risk from Baseline | | | --- | --- | --- | --- | --- | --- | | | | HR | p-value2 | HR | p-value2 | | Baseline LDH (IU/mL)1,3 | | 1.002 | 0.003 | 1.004 | <0.001 | | Baseline Alkaline Phosphatase (IU/mL)1,3 | | --- | --- | 1.00 | 0.780 | | Line of Therapy (1stthrough 6th) | | 1.37 | 0.001 | 1.35 | 0.035 | | Type of Therapy (Taxotere: Yes/No) | | 0.80 | 0.278 | 1.45 | 0.276 | | 9 - 12 Week CTC (<5 vs. ≥5) | 125 | 1.74 | 0.015 | 3.94 | <0.001 | | 9 - 12 Week PSA Reduction from Baseline (≥30% vs. <30%)1 | | 2.23 | <0.001 | 1.46 | 0.221 | | Baseline ECOG Status (0 vs. 1 vs. 2) | | 1.21 | 0.307 | 1.89 | 0.004 | | Baseline Hemoglobin (g/dL)3 | | 0.93 | 0.322 | 0.97 | 0.758 | | Baseline LDH (IU/mL)1,3 | | 1.00 | 0.190 | 1.003 | <0.001 | | Baseline Alkaline Phosphatase (IU/mL)1,3 | | --- | --- | 1.00 | 0.989 | | Line of Therapy (1stthrough 6th) | | 1.25 | 0.052 | 1.11 | 0.499 | | Type of Therapy (Taxotere: Yes/No) | | 0.97 | 0.903 | 1.26 | 0.486 | | 13 - 20 Week CTC (<5 vs. ≥5) | 123 | 2.95 | <0.001 | 3.75 | 0.001 | | 13-20 Week PSA Reduction from Baseline (≥30% vs. <30%)1 | | 1.97 | 0.002 | 1.52 | 0.275 | | Baseline ECOG Status (0 vs. 1 vs. 2) | | 0.98 | 0.919 | 1.98 | 0.002 | | Baseline Hemoglobin (g/dL)3 | | 1.03 | 0.723 | 0.87 | 0.232 | | Baseline LDH (IU/mL)1,3 | | 1.00 | 0.380 | 1.003 | <0.001 | | Baseline Alkaline Phosphatase (IU/mL)1,3 | | --- | --- | 1.00 | 0.078 | | Line of Therapy (1stthrough 6th) | | 1.25 | 0.050 | 1.06 | 0.751 | | Type of Therapy (Taxotere: Yes/No) | | 1.04 | 0.882 | 0.90 | 0.770 | 1 Determined from Serum Drawn on the Same Date as the Blood Drawn for CTC ${}^{2}$ p-value from Wald test of Z statistic 3 Assessed as a continuous parameter # Use of CTC to Monitor Clinical Status of Metastatic Prostate Cancer Patients # Relationship between survival, CTCs and disease assessment by PSA At present, a reduction in PSA is one of the primary means to determine response to therapy in MPC patients. To establish the relationship of clinical status as determined by a PSA to CTC, reduction of $\geq 30\%$ or $\geq 50\%$ PSA and CTC were measured 2-5 weeks, 6-8 weeks, 9-12 weeks and 13-20 weeks after initiation of therapy and compared to overall survival. For the Kaplan-Meier analysis the elapsed OS times were calculated from the time of blood draw. Patients were segmented into Favorable groups based upon a CTC of $&lt; 5$ at the time of evaluation and a $\geq 30\%$ reduction of PSA from baseline to the time of evaluation. Patients were segmented into Unfavorable groups based upon a CTC of $\geq 5$ and $&lt; 30\%$ reduction of PSA from baseline to the time of evaluation. Figure 9 shows the results of the analysis 2-5 weeks after initiation of therapy, Figure 10 the analysis 6-8 weeks after initiation of therapy, Figure 11 the analysis 9-12 weeks after initiation of therapy and Figure 12 the analysis 13-20 weeks after initiation of therapy. {22}  Figure 9: OS of MPC Patients 2-5 weeks after the Initiation of Therapy A. 2-5 Week CTC  B. $\geq 30\%$ PSA Reduction at 2-5 Weeks Figure 10: OS of MPC Patients 6-8 weeks after the Initiation of Therapy  A. 6-8 Week CTC {23}  B. $\geq 30\%$ PSA Reduction at 6-8 Weeks  Figure 11: OS of MPC Patients 9-12 weeks after the Initiation of Therapy  A. 9-12 Week CTC {24}  Figure 12: OS of MPC Patients 13-20 weeks after the Initiation of Therapy A. 13-20 Week CTC  B. $\geq 30\%$ PSA Reduction at 13-20 Weeks Table 9 illustrates the comparison of median overall survival at different time points after therapy with CTC, a $30\%$ PSA reduction and a $50\%$ PSA reduction. Table 9: Comparison of Median OS between Favorable and Unfavorable CTC and PSA Reduction Groups. | Time Point | CTC / 7.5mL | | | | | 30% PSA Reduction from Baseline | | | | | 50% PSA Reduction from Baseline | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | | N | ≥5 (%) | Median OS <5 | ≥5 | logrank p-value | HR | N | <30% (%) | Median OS ≥30% | <30% | logrank p-value | HR | N | <50% (%) | Median OS ≥50% | <50% | | 2-5 Weeks | 203 | 39% | 20.7 | 9.5 | <0.0001 | 4.5 | 207 | 71% | 17.2 | 15.2 | 0.3653 | 1.2 | 207 | 83% | 17.5 | 16.2 | | 6-8 Weeks | 163 | 33% | 19.9 | 8.5 | <0.0001 | 3.6 | 167 | 60% | 22.8 | 11.5 | 0.0011 | 2.2 | 167 | 75% | 22.8 | 14.4 | {25} | | CTC / 7.5mL | | | | | | 30% PSA Reduction from Baseline | | | | | | 50% PSA Reduction from Baseline | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | Time Point | N | ≥5 (%) | Median OS <5 | ≥5 | logrank p-value | HR | N | <30% (%) | Median OS ≥30% | <30% | logrank p-value | HR | N | <50% (%) | Median OS ≥50% | <50% | logrank p-value | HR | | 9-12 Weeks | 149 | 33% | 19.6 | 7.6 | <0.0001 | 5.3 | 155 | 46% | 18.5 | 10.2 | 0.0007 | 2.2 | 155 | 59% | 19.6 | 10.8 | 0.0006 | 2.3 | | 13-20 Weeks | 143 | 31% | 19.8 | 6.7 | <0.0001 | 6.5 | 142 | 41% | 17.7 | 8.7 | <0.0001 | 2.9 | 142 | 46% | 17.7 | 9.9 | 0.0001 | 2.6 | # Concordances between CTC and PSA Changes in MPC Patients The data in Figure 9 through 12 and in Table 9, illustrate a highly significant difference in overall survival between patients with Unfavorable CTC and Favorable CTC at all time points tested, whereas PSA evaluations were not significant until 6-8 weeks after the initiation of therapy. Although the differences in median OS between the Favorable $(\geq 30\%$ or $\geq 50\%$ PSA reduction from baseline) and Unfavorable $(&lt; 30\%$ or $&lt; 50\%$ PSA reduction from baseline) PSA reduction groups were significant, the separation between the Favorable $(&lt; 5$ CTC) and Unfavorable $(\geq 5$ CTC) CTC groups appeared greater and was significant at all time points after the initiation of therapy. At present, either a $\geq 30\%$ or $\geq 50\%$ reduction in PSA is commonly used to evaluate disease progression in metastatic prostate cancer patients. Therefore, to establish the relationship between CTC and changes in PSA two by two tabulations of concordant and discordant observations between CTC and PSA changes for each time point after the initiation of therapy were constructed. Although comparisons of CTC to PSA change at both magnitudes were calculated, only data from the CTC vs. $\geq 30\%$ PSA change are reported. This decision was based on a recent publication (J Nat Ca Inst. 98 (8):p.516-521, 2006) demonstrating that a 3-month $30\%$ PSA decline showed a stronger association with decrease in risk of death than did a $50\%$ decrease in PSA. Furthermore, a comparison of patient-wise and observation-wise results from the $30\%$ and $50\%$ PSA decline vs. CTC analyses did not demonstrate substantial differences in the Positive % Agreement, Negative % Agreement and Overall Agreement at any of the observed time points. A total of 197, 159, 146, and 138 patients had serum samples analyzed by the central laboratory and had evaluable CTC results 2-5 weeks, 6-8 weeks, 9-12 weeks, and 13-20 weeks after the initiation of therapy, respectively. To determine a patient's response to therapy, the percent change in PSA from the baseline value was calculated for each of the time points after the initiation of therapy. For PSA changes at each time point, the Favorable group was defined as patients with a $\geq 30\%$ reduction in PSA and the Unfavorable group was defined as patients with a $&lt; 30\%$ reduction in PSA. For CTC at each time point, the Favorable group was defined as patients having $&lt; 5$ CTC per $7.5\mathrm{mL}$ of blood and the Unfavorable group was defined as patients having $\geq 5$ CTC. Because CTC vs. PSA results of the patient-wise comparisons between CTC and a $\geq 30\%$ PSA reduction at 2-5 weeks and 13-20 weeks after the initiation of therapy showed the most significant discordance and concordance, respectively, these data are presented in Table 10 and Table 11, respectively. {26} Table 10: MPC Patient-Wise Comparison of CTC and ${30}\%$ PSA Reduction at 2-5 Weeks | % Reduction in PSA from Baseline at 2-5 Weeks After Initiation of Therapy | CTCs 2-5 Weeks after the Initiation of Therapy | | Total | | --- | --- | --- | --- | | | < 5 CTCs/7.5mL | ≥ 5 CTCs/7.5mL | | | ≥30% Reduction in PSA | 50 | 11 | 61 | | <30% Reduction in PSA | 69 | 67 | 136 | | Total | 119 | 78 | 197 | | Measurement | Estimate | Lower 95% CI | Upper 95% CI | | --- | --- | --- | --- | | Positive % Agreement | 49% | 41% | 58% | | Negative % Agreement | 82% | 70% | 91% | | Positive Predictive Value | 86% | 76% | 93% | | Negative Predictive Value | 42% | 33% | 51% | | Overall Agreement | 59% | 52% | 66% | | Odds Ratio | 4.4 | 2.1 | 9.2 | Table 11: MPC Patient-Wise Comparison of CTC and ${30}\%$ PSA Reduction at 13-20 Weeks. | % Reduction in PSA from Baseline at 13-20 Weeks After Initiation of Therapy | CTC 13-20 Weeks after the Initiation of Therapy | | Total | | --- | --- | --- | --- | | | < 5 CTC | ≥ 5 CTC | | | ≥30% Reduction in PSA | 72 | 9 | 81 | | <30% Reduction in PSA | 23 | 34 | 57 | | Total | 95 | 43 | 138 | | Measurement | Estimate | Lower 95% CI | Upper 95% CI | | --- | --- | --- | --- | | Positive % Agreement | 60% | 46% | 72% | | Negative % Agreement | 89% | 80% | 95% | | Positive Predictive Value | 79% | 64% | 90% | | Negative Predictive Value | 76% | 66% | 84% | | Overall Agreement | 77% | 69% | 84% | | Odds Ratio | 11.8 | 4.9 | 28.3 | The results of an "observation-wise" comparison of CTC and PSA changes using a $\geq 30\%$ reduction threshold at 2-5 weeks, 6-8 weeks, 9-12 weeks, and 13-20 weeks after the initiation of therapy combined are shown in Table 12. {27} Table 12: MPC Observation-Wise Comparison of CTC and ${30}\%$ PSA Reduction. | % Reduction in PSA from Baseline After Initiation of Therapy | CTC after the Initiation of Therapy | | Total | | --- | --- | --- | --- | | | < 5 CTC | ≥ 5 CTC | | | ≥30% Reduction in PSA | 243 | 41 | 284 | | <30% Reduction in PSA | 175 | 181 | 356 | | Total | 418 | 222 | 640 | | Measurement | Estimate | Lower 95% CI | Upper 95% CI | | --- | --- | --- | --- | | Positive % Agreement | 51% | 46% | 56% | | Negative % Agreement | 86% | 81% | 89% | | Positive Predictive Value | 82% | 76% | 86% | | Negative Predictive Value | 58% | 53% | 63% | | Overall Agreement | 66% | 62% | 70% | | Odds Ratio | 6.1 | 4.1 | 9.1 | The overall concordance between CTC and PSA changes at the various time points after the initiation of therapy ranged from $59\%$ to $77\%$ when comparing to a $\geq 30\%$ PSA reduction and from $52\%$ to $75\%$ when comparing to a $\geq 50\%$ PSA reduction, showing that there was discordance between CTC and PSA changes in $\sim 25\%$ to $40\%$ of the patients. # CTC Levels and PSA Reduction Combined to Predict OS in MPC Patients To determine which of the discordant results better reflected the prognosis of the patient, CTC assessment and changes in PSA 2-5 weeks, 6-8 weeks, 9-12 weeks and 13-20 weeks after initiation of therapy were compared to overall survival. Elapsed OS times were calculated from the blood draw being evaluated. For the Kaplan-Meier analysis Figure 13 (Panels A, B, C and D) patients were segmented into four groups based upon their CTC counts and PSA reduction at 2-5 weeks, 6-8 weeks, 9-12 weeks, and 13-20 weeks after the initiation of therapy, respectively: - Group 1 (green curve), patients with $&lt;5$ CTC at the time of evaluation and a $\geq 30\%$ reduction of PSA from baseline to the time of evaluation; - Group 2 (blue curve), patients with $&lt;5$ CTC at the time of evaluation and a $&lt;30\%$ reduction of PSA from baseline to the time of evaluation; - Group 3 (orange curve), patients with $\geq 5$ CTC at the time of evaluation and a $\geq 30\%$ reduction of PSA from baseline to the time of evaluation - Group 4 (red curve), patients with $\geq 5$ CTC at the time of evaluation and a $&lt;30\%$ reduction of PSA from baseline to the time of evaluation. {28}  Figure 13: CTC Levels and PSA Changes Combined to Predict OS 2-5 Weeks (Panel A), 6-8 Weeks (Panel B), 9-12 Weeks (Panel C), and 13-20 Weeks (Panel D) After the Initiation of Therapy A. 2-5 Weeks  B. 6-8 Weeks {29}  C. 9-12 Weeks  D. 13-20 Weeks {30} Figure 13 shows that patients with $\geq 5$ CTC at any point after the initiation of therapy had a much higher likelihood of dying sooner, irrespective of the changes in PSA levels from baseline. Patients with $\geq 5$ CTC at all time points (Group 3 and Group 4) had the shortest median overall survivals, which were not significantly different. However, the median OS of these two groups was significantly different compared to the median OS of the patients with $&lt; 5$ CTC at all time points (Group 1 and Group 2). These two groups (Group 1 and Group 2) had the longest median overall survivals, which were not significantly different. The important finding illustrated in Figure 13 is that although a reduction of PSA at some points after initiation of therapy may reach significance for prediction of survival, Favorable CTC at any time point were more accurate than the PSA evaluation. The practical implication is the use of CTC analysis for the evaluation of the probability of survival of MPC patients. In cases where CTC and PSA change were discordant, CTC provided the most accurate assessment of prognosis. 4. Clinical cut-off: $&lt; 5$ CTC per $7.5\,\mathrm{mL}$ blood. 5. Expected values/Reference range: Not applicable. N. Proposed Labeling: The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10. O. Conclusion: The submitted information in this premarket notification is complete and supports a substantial equivalence decision. 31