Primary resistance in docetaxel and androgen deprivation therapy in metastatic castrate sensitive prostate cancer patients.

Abstract

342 Background: Docetaxel chemotherapy combined with androgen deprivation therapy (ADT) has become the new standard of care in patients with metastatic castrate sensitive prostate cancer as it has shown significant benefit in terms of overall survival (OS) and response rates (Sweeney 2015, James 2016). However a subgroup of patients still experience early progression. Methods: We searched the hospital database for patients treated with docetaxel in the castrate sensitive setting. Eligible patients included those with newly diagnosed metastatic prostate adenocarcinoma and also patients with relapsed metastatic disease post radical radiotherapy or radical prostatectomy. Patients starting chemotherapy > 12 weeks after commencing ADT were excluded. Results: We identified 72 patients treated with docetaxel and ADT between August 2014 and September 2017. The median age was 66 years (49-84 years). Of the 72 patients, 63 (88%) had bone metastases, 5 (7%) had visceral metastases and 45 (63%) had pelvic lymph node disease. Seven patients (9.7%) had relapsed metastatic disease post radical treatment. All patients had ≤6 cycles of docetaxel. Median time from diagnosis of metastatic disease to commencing castrate resistant treatment was 13 months (2-41 months). Median duration of follow-up was 16 months (5-39 months). Six patients (8%) had biochemical, radiological or clinical progression during, or at completion of docetaxel chemotherapy. One patient terminated treatment before completion of six cycles due to disease progression. The median presenting PSA in this group was 49.5 ug/L (9.04-2290 ug/L) and 2 patients had visceral disease. Of these 6 patients, 2 have died, and the median OS for the group was 11.5 months (8-22 months). Five patients were subsequently treated with enzalutamide and 1 with abiraterone. Conclusions: Despite the improvement in OS and response rates with the use of early docetaxel, a clinically significant number of patients developed disease progression during treatment, and these patients have a particularly poor prognosis. These patients should be the focus of future clinical trials.