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PURPOSE: To determine whether reverse transcriptase polymerase chain reaction (RT-PCR) to detect circulating prostate-specific antigen (PSA)-positive cells is a prognostic factor for survival in hormone refractory prostate cancer and to validate the prognostic importance of this test in relation to other known prognostic factors. PATIENTS AND METHODS: A single centralized laboratory received and analyzed whole blood for RT-PCR for PSA for a subset of patients enrolled on two Cancer and Leukemia Group B (CALGB) randomized trials (CALGB 9583 and CALGB 9480). Using 9583, a prognostic model was developed and an independent data set (CALGB 9480) was used to validate the fitted model. RESULTS: Of 162 patients in 9583, 91 (56%) patients were negative for RT-PCR for PSA and 71 (44%) patients were positive. The median survival time was 21 months (95% confidence interval CI, 18 to 27 months) for RT-PCR-negative patients compared with 11 months (95% CI, 8 to 15 months) for RT-PCR-positive patients (P < or =.001). In multivariable analysis, the hazard ratio (HR) for death was 1.7 (95% CI, 1.2 to 2.4; P =.006) for positive RT-PCR patients compared with negative RT-PCR patients. A fitted model that incorporated RT-PCR for PSA and other factors was used to classify patients from 9480 into one of two risk groups: low or high. We observed good agreement between the observed and predicted survival probabilities for the two risk groups. CONCLUSION: RT-PCR to detect PSA-positive circulating cells is confirmed to be a significant prognostic factor of survival in patients with hormone refractory prostate cancer. This model could be used to stratify patients in randomized phase III trials.
Halabi et al. (2003) studied this question.