Prostate-specific antigen flare phenomenon with docetaxel-based chemotherapy in patients with androgen-independent prostate cancer

OBJECTIVE: To evaluate the prostate-specific antigen (PSA) 'flare' phenomenon in patients with androgen-independent prostate cancer (AIPC) treated with docetaxel, as flare is a known effect of androgen-deprivation therapy in hormone-dependent prostate cancer. PATIENTS AND METHODS: The charts of 56 patients who received docetaxel-based chemotherapy in three different centres from August 1999 to August 2007 were reviewed retrospectively. The biochemical response was characterized according to the Bubley criteria. There was an immediate PSA response (PSA decline ≥ 50%) in 23 (41%) patients, PSA stabilization (PSA decline < 50%) in 16 (29%) and PSA progression in nine (16%). There was also a fourth response, i.e. PSA flare, defined as an increase in PSA level with no symptomatic progression, after starting docetaxel-based chemotherapy administered every 3 weeks. RESULTS: Eight (14%) patients with PSA flare were identified; all had osseous disease and five had additional soft-tissue disease. The PSA flare lasted a median (range) of 21 (21-42) days and it spread over a median of 1 (1-2) cycles. The temporary PSA surge exceeded baseline values by a median (range) of 61.5 (12-404)%. There was a subsequent PSA response in six of the eight patients and PSA stabilized in the remaining two. Patients with flare received a median of 8.5 (5-12) treatment cycles, vs a median of 8 (2-12) in the immediate PSA response group (P = 0.103, Student's t-test). The Response Evaluation Criteria in Solid Tumors criteria evaluation showed one patient with a partial response and six with stable disease. The median survival of patients with PSA flare was 12.5 months, while that of the immediate PSA responders was 20.1 months (not statistically significant, P = 0.168, log-rank test). CONCLUSION: Of patients with AIPC, 14% had an initial PSA flare after starting docetaxel-based chemotherapy. The occurrence of PSA flare had no effect on treatment duration or outcome. With lack of clinical progression, docetaxel-based chemotherapy should be administered for at least two 3-week cycles before further decisions are made about efficacy.