Multiple cycles of intermittent chemotherapy in metastatic androgen-independent prostate cancer

Recently, completed phase III studies demonstrated a survival benefit for a fixed number of cycles of docetaxel-containing chemotherapy treatment of androgen-independent prostate cancer (AIPC). Management of patients who respond well to initial chemotherapy for AIPC remains ill-defined. We previously reported that in a select group of such patients, retreatment with the same regimen was feasible and was associated with quality of life gains. Here, we report that multiple cycles of such intermittent chemotherapy are feasible. We prospectively tested intermittent chemotherapy in eight AIPC patients responding to calcitriol plus docetaxel who reached a serum prostate-specific antigen (PSA) <4 ng ml^-1 (22% of the 37 patients who were initially treated with this regimen). Chemotherapy was suspended until a rise in PSA ≥50% and 1 ng ml^-1. The median duration of the first treatment holiday was 20 weeks (13-74 weeks) and all patients retained sensitivity to retreatment. Four patients were eligible for a second chemotherapy holiday, and the median duration was 21 weeks (17-28 weeks). Two patients elected to take a third chemotherapy holiday, which lasted 10 and 28 weeks. The median time to treatment failure was 26.5 months (95% CI 23.6-29.4 months), and the median survival is 41 months (95% CI 33.7-48.3 months). Multiple cycles of intermittent chemotherapy interrupted by clinically meaningful treatment holidays are feasible in a subset of AIPC patients treated with this docetaxel-containing regimen. Intermittent chemotherapy for AIPC is feasible and deserves further study.