We tested the hypothesis that the level of circulating tumor cells can predict survival in metastatic breast cancer. In a prospective, multicenter study, we tested 177 patients with measurable metastatic breast cancer for levels of circulating tumor cells both before the patients were to start a new line of treatment and at the first follow-up visit. The progression of the disease or the response to treatment was determined with the use of standard imaging studies at the participating centers. Outcomes were assessed according to levels of circulating tumor cells at baseline, before the patients started a new treatment for metastatic disease. Patients in a training set with levels of circulating tumor cells equal to or higher than 5 per 7.5 ml of whole blood, as compared with the group with fewer than 5 circulating tumor cells per 7.5 ml, had a shorter median progression-free survival (2.7 months vs. 7.0 months, P18 months, P<0.001). At the first follow-up visit after the initiation of therapy, this difference between the groups persisted (progression-free survival, 2.1 months vs. 7.0 months; P18 months; P<0.001), and the reduced proportion of patients (from 49 percent to 30 percent) in the group with an unfavorable prognosis suggested that there was a benefit from therapy. The multivariate Cox proportional-hazards regression showed that, of all the variables in the statistical model, the levels of circulating tumor cells at baseline and at the first follow-up visit were the most significant predictors of progression-free and overall survival. The number of circulating tumor cells before treatment is an independent predictor of progression-free survival and overall survival in patients with metastatic breast cancer.

Purpose: The purpose of this study was to determine the accuracy, precision, and linearity of the CellSearch system and evaluate the number of circulating tumor cells (CTCs) per 7.5 mL of blood in healthy subjects, patients with nonmalignant diseases, and patients with a variety of metastatic carcinomas. Experimental Design: The CellSearch system was used to enumerate CTCs in 7.5 mL of blood. Blood samples spiked with cells from tumor cell lines were used to establish analytical accuracy, reproducibility, and linearity. Prevalence of CTCs was determined in blood from 199 patients with nonmalignant diseases, 964 patients with metastatic carcinomas, and 145 healthy donors. Results: Enumeration of spiked tumor cells was linear over the range of 5 to 1,142 cells, with an average recovery of ≥85% at each spike level. Only 1 of the 344 (0.3%) healthy and nonmalignant disease subjects had ≥2 CTCs per 7.5 mL of blood. In 2,183 blood samples from 964 metastatic carcinoma patients, CTCs ranged from 0 to 23,618 CTCs per 7.5 mL (mean, 60 ± 693 CTCs per 7.5 mL), and 36% (781 of 2,183) of the specimens had ≥2 CTCs. Detection of ≥2 CTCs occurred at the following rates: 57% (107 of 188) of prostate cancers, 37% (489 of 1,316) of breast cancers, 37% (20 of 53) of ovarian cancers, 30% (99 of 333) of colorectal cancers, 20% (34 of 168) of lung cancers, and 26% (32 of 125) of other cancers. Conclusions: The CellSearch system can be standardized across multiple laboratories and may be used to determine the clinical utility of CTCs. CTCs are extremely rare in healthy subjects and patients with nonmalignant diseases but present in various metastatic carcinomas with a wide range of frequencies.

Purpose: A method for enumerating circulating tumor cells (CTC) has received regulatory clearance. The primary objective of this prospective study was to establish the relationship between posttreatment CTC count and overall survival (OS) in castration-resistant prostate cancer (CRPC). Secondary objectives included determining the prognostic utility of CTC measurement before initiating therapy, and the relationship of CTC to prostate-specific antigen (PSA) changes and OS at these and other time points. Experimental Design: Blood was drawn from CRPC patients with progressive disease starting a new line of chemotherapy before treatment and monthly thereafter. Patients were stratified into predetermined Favorable or Unfavorable groups (<5 and ≥5 CTC/7.5mL). Results: Two hundred thirty-one of 276 enrolled patients (84%) were evaluable. Patients with Unfavorable pretreatment CTC (57%) had shorter OS (median OS, 11.5 versus 21.7 months; Cox hazard ratio, 3.3; P < 0.0001). Unfavorable posttreatment CTC counts also predicted shorter OS at 2 to 5, 6 to 8, 9 to 12, and 13 to 20 weeks (median OS, 6.7-9.5 versus 19.6-20.7 months; Cox hazard ratio, 3.6-6.5; P < 0.0001). CTC counts predicted OS better than PSA decrement algorithms at all time points; area under the receiver operator curve for CTC was 81% to 87% and 58% to 68% for 30% PSA reduction (P = 0.0218). Prognosis for patients with (a) Unfavorable baseline CTC who converted to Favorable CTC improved (6.8 to 21.3 months); (b) Favorable baseline CTC who converted to Unfavorable worsened (>26 to 9.3 months). Conclusions: CTC are the most accurate and independent predictor of OS in CRPC. These data led to Food and Drug Administration clearance of this assay for the evaluation of CRPC.

Purpose: As treatment options expand for metastatic colorectal cancer (mCRC), a blood marker with a prognostic and predictive role could guide treatment. We tested the hypothesis that circulating tumor cells (CTCs) could predict clinical outcome in patients with mCRC. Patients and Methods: In a prospective multicenter study, CTCs were enumerated in the peripheral blood of 430 patients with mCRC at baseline and after starting first-, second-, or third-line therapy. CTCs were measured using an immunomagnetic separation technique. Results: Patients were stratified into unfavorable and favorable prognostic groups based on CTC levels of three or more or less than three CTCs/7.5 mL, respectively. Patients with unfavorable compared with favorable baseline CTCs had shorter median progression-free survival (PFS; 4.5 v 7.9 months; P = .0002) and overall survival (OS; 9.4 v 18.5 months; P < .0001). Differences persisted at 1 to 2, 3 to 5, 6 to 12, and 13 to 20 weeks after therapy. Conversion of baseline unfavorable CTCs to favorable at 3 to 5 weeks was associated with significantly longer PFS and OS compared with patients with unfavorable CTCs at both time points (PFS, 6.2 v 1.6 months; P = .02; OS, 11.0 v 3.7 months; P = .0002). Among nonprogressing patients, favorable compared with unfavorable CTCs within 1 month of imaging was associated with longer survival (18.8 v 7.1 months; P < .0001). Baseline and follow-up CTC levels remained strong predictors of PFS and OS after adjustment for clinically significant factors. Conclusion: The number of CTCs before and during treatment is an independent predictor of PFS and OS in patients with metastatic colorectal cancer. CTCs provide prognostic information in addition to that of imaging studies.

Purpose: Metastatic breast cancer (MBC) is incurable; its treatment is palliative. We investigated whether the presence of circulating tumor cells (CTCs) predicts treatment efficacy, progression-free survival (PFS), and overall survival (OS) in patients with newly diagnosed MBC who were about to start first-line therapy. Patients and Methods: One hundred seventy-seven patients with measurable MBC were enrolled onto a prospective study. Eighty-three of the 177 patients were entering first-line treatment, and these patients are the focus of this analysis. CTCs from 7.5 mL of whole blood drawn before treatment initiation (baseline) and monthly thereafter for up to 6 months were isolated and enumerated using immunomagnetics. Results: The mean (± standard deviation) follow-up time was 11.1 ± 4.4 months (median, 12.2 months). Forty-three patients (52%) had ≥ five CTCs at baseline. The median PFS was 7.2 months (95% CI, 4.9 to 9.4 months), and the median OS was more than 18 months. Patients with ≥ five CTCs at baseline and at first follow-up (4 weeks) had a worse prognosis than patients with less than five CTCs (baseline: median PFS, 4.9 v 9.5 months, respectively; log-rank, P = .0014; median OS, 14.2 v > 18 months, respectively; log-rank, P = .0048; first follow-up: median PFS, 2.1 v 8.9 months, respectively; log-rank, P = .0070; median OS, 11.1 v > 18 months, respectively; log-rank, P = .0029). CTCs before and after the initiation of therapy were strong, independent prognostic factors. Conclusion: Detection of CTCs before initiation of first-line therapy in patients with MBC is highly predictive of PFS and OS. This technology can aid in appropriate patient stratification and design of tailored treatments.

Purpose: We reported previously that ≥5 circulating tumor cells (CTC) in 7.5 mL blood at baseline and at first follow-up in 177 patients with metastatic breast cancer (MBC) were associated with poor clinical outcome. In this study, additional follow-up data and CTC levels at subsequent follow-up visits were evaluated. Experimental Design: CTCs were enumerated in 177 MBC patients before the initiation of a new course of therapy (baseline) and 3 to 5, 6 to 8, 9 to 14, and 15 to 20 weeks after the initiation of therapy. Progression-free survival (PFS) and overall survival (OS) times were calculated from the dates of each follow-up blood draw. Kaplan-Meier plots and survival analyses were done using a threshold of ≥5 CTCs/7.5 mL at each blood draw. Results: Median PFS times for patients with <5 CTC from each of the five blood draw time points were 7.0, 6.1, 5.6, 7.0, and 6.0 months, respectively. For patients with ≥5 CTC, median PFS from these same time points was significantly shorter: 2.7, 1.3, 1.4, 3.0, and 3.6 months, respectively. Median OS for patients with 18.5 months. For patients with ≥5 CTC, median OS from these same time points was significantly shorter: 10.9, 6.3, 6.3, 6.6, and 6.7 months, respectively. Median PFS and OS times at baseline and up to 9 to 14 weeks after the initiation of therapy were statistically significantly different. Conclusions: Detection of elevated CTCs at any time during therapy is an accurate indication of subsequent rapid disease progression and mortality for MBC patients.