Circulating Tumor Cells in Biochemical Recurrence of Prostate Cancer

Objective: Circulating tumor cells (CTCs) have known prognostic implications in metastatic castration-resistant prostate cancer, but little is known regarding its utility in biochemical recurrence (BR) of prostate cancer. The primary objectives were to determine whether CTCs are measurable in patients with BR and whether it can reliably predict prostate-specific antigen (PSA) increase and PSA doubling times (PSADTs). Methods: BR was identified in patients after prostatectomy or radiation or both, with a PSA increase of ≥ 0.2 for prior prostatectomy or > 2 mg/dL increase for post-nadir in prior radiotherapy. CTCs were enumerated at baseline at the time of study entry using the CellSearch (Janssen Diagnostics, Raritan, NJ) test. Results: The median age for all 36 patients accrued was 69.5 years (range, 51-91) with a median PSA of 1.65 ng/mL (range, 0.2-65.8). Gleason scores ranged from 5 to 9 (median, 7). The majority had prostatectomy (n = 25), external beam radiotherapy (n = 9), CyberKnife (Accuray, Sunnyvale, CA) (n = 1), and combined radiohormonal therapy (n = 1). PSADT ranged from 0.35 to 55 months, with a median of 7.43 months. The incidence of positive CTCs was 8.3% (3 patients), of whom 2 had biopsy-proven bony lesions on presenting with equivocal scans and PSADTs of 2.27 and 3.08 months, respectively. The third CTC-positive patient had a PSADT of 4.99 months. Conclusions: Obtaining CTCs in unselected patients presenting with BR has a relatively low yield. However, obtaining a positive CTC raises the suspicion of the presence of metastatic disease and may have utility for longitudinal follow-ups of patients with BR.