Timing of PSA response to guide cessation of docetaxel in prostate cancer.

Abstract

e16069 Background: Docetaxel plus prednisolone is an established treatment for men with advanced prostate cancer. Clinicians need to be able to identify men who are not benefiting from chemotherapy, and a key unanswered question is how many cycles of docetaxel should men receive before this assessment is made. We investigated the prognostic significance of a PSA response to docetaxel chemotherapy and the number of cycles after which an absence of PSA response could reliably predict future non-response. Methods: Data was collected for men who received one to ten cycles of docetaxel for castrate refractory prostate cancer between 2005 and 2011. PSA was monitored during treatment. All men were treated at a single centre, The Christie NHS Foundation Trust, UK. Survival is defined as the interval between the first dose of docetaxel and the date of death. Results: Data was available for 320 patients. At the commencement of chemotherapy, median age was 67 years (range 49-81yrs) and median PSA was 207ng/ml. All patients had a Karnofsky Performance Status ≥ 70%. There were 239 deaths and the median survival of the whole group was 403 days. 140 (44%) patients received 6 cycles of docetaxel and 23 patients (7%) received 10 cycles. Median survival was significantly longer in men who had any fall in PSA during chemotherapy compared to those whose PSA did not fall (462 days vs 268 days, p<0.001). Any PSA fall occurred during the first 4 cycles of docetaxel for 95.1% of men. Median survival was significantly longer in men who had a 50% fall in PSA during chemotherapy compared to those who did not (491 vs 357 days, p<0.001). The 50% fall in PSA occurred during the first 5/6 cycles of chemotherapy in 91.5% and 97.7% of men respectively. Conclusions: A patient’s clinical condition is of paramount importance when assessing them during docetaxel chemotherapy. Our data suggest that a fall in PSA following docetaxel is an indicator of improved overall survival. PSA response could help clinicians decide when to stop docetaxel; patients are unlikely to have a fall in PSA if it has not occurred during the first 4 cycles of chemotherapy and they fall into a poor prognostic group. These patients should be considered for alternative treatment in order to improve outcomes and spare them unnecessary toxicity.