Time to prostate specific antigen (PSA) nadir may predict rapid relapse in men with metastatic castration-resistant prostate cancer (CRPC) receiving docetaxel chemotherapy

Docetaxel has been shown to improve survival in patients with metastatic castrate-resistant prostate cancer (mCRPC). There is no clear consensus regarding the optimum duration of chemotherapy. If patients at greater risk of rapid disease relapse could be identified when on chemotherapy, appropriate follow-up strategies could be put into place. The aim of our study was to find prostate specific antigen (PSA) characteristics that predict a shorter disease response to docetaxel chemotherapy. Data from 41 consecutive mCRPC patients treated with three-weekly docetaxel chemotherapy at a single centre between February 2010 and February 2012 were retrospectively analysed. All patients had >= 50 % reduction in their PSA with chemotherapy. The relationship between time to PSA nadir (TTN) and PSA halving time with time to PSA progression and overall chemotherapy response duration was analysed. TTN was a strong predictor of the duration of chemotherapy response and time to PSA progression. When TTN was >= 16 weeks, the mean duration of response to chemotherapy was 37.5 weeks compared to 19.9 weeks when TTN <16 weeks (95 % CI, 12.66-22.60; p = 1.239 x 10(-8)). The mean time to PSA progression was 12.8 weeks if TTN was >= 16 weeks and 8.2 weeks TTN was <16 weeks (95 % CI 0.63-8.60; p = 0.024). We observed that a TTN from the initiation of chemotherapy of <16 weeks for patients with mCRPC is an independent predictor of shorter duration of response and shorter progression-free survival.