Updated analysis of a pilot study examining the role of circulating tumor cells (CTCs) in biochemical recurrence (BR) of prostate cancer.

Abstract

e15023 Background: CTCs have been used as a prognostic factor in metastatic prostate cancer. Little data exists regarding the role of CTCs in BR of prostate cancer. The primary aim of this study was to determine whether there is a correlation between the number of CTCs with prostate specific antigen (PSA) levels and PSA doubling time (PSADT) in men with BR. In addition, we wished to explore the correlation of the CTCs with clinical and laboratory factors (Gleason scores, testosterone, hemoglobin, alkaline phosphatase, BMI, imaging results). Methods: BR was defined as patients (pts) who have undergone primary treatment with prostatectomy or radiation or both, with rise to ≥ 0.2 from a prior undetectable level for prior prostatectomy or > 2 mg/dl rise from post-nadir radiotherapy. The study was powered to detect a Pearson correlation of .46 with a sample size of 36. 16 of planned accrual of 36 pts were enrolled from May to December 2010. PSADT was obtained and correlated with the CTC values, categorized as PSADT of < 3 mos, 3-14.9 mos and > 15 mos. CTCs were evaluated in 7.5 mL of peripheral blood using the CTC CellSearch test. Results: Median age for 16 patients was 71.5 (range: 57 – 91); median PSA of 1.6 ng/mL (range 0.2 – 65.8); testosterone levels of 304 ng/dL (range: 31 – 600). Gleason scores ranged from 5 to 8. Prostatectomy was the primary treatment in 9 pts, radiotherapy in 5 pts, Cyberknife in 1 pt and combined radiohormones in 1 pt. Median hemoglobin was 12.81 g/dL, BMI was 27.1 and alkaline phosphatase was 68 IU/L. PSADT varied between 2.27 to 55 months, with a median of 9.6 mos. All pts accrued had 0 CTC levels except one who had a CTC of 1 but found to have biopsy-proven isolated metastatic bony lesion, with the shortest PSADT of 2.27 and an absolute PSA level of 5.6 ng/ml. Conclusions: Most prostate cancer pts with BR have negative blood CTCs but the small sample precludes a formal assessment of the correlation of CTC levels with PSADT and PSA. However, the only pt with a positive CTC also had the most rapid PSADT out of 16 pts, raising the possibility that obtaining a positive CTC may herald onset of metastatic disease and may have utility for longitudinal follow-ups of pts with BR. Supported by IRG-08-091-01 from ACS to GWUCI.