The Influence of Prednisone on the Efficacy of Docetaxel in Men with Metastatic Castration-Resistant Prostate Cancer

BACKGROUND: Prednisone and other corticosteroids can provide palliation and tumor responses in patients with prostate cancer. The combination of docetaxel and prednisone was the first treatment shown to prolong survival in men with metastatic castration-resistant prostate cancer (mCRPC). Since the approval of docetaxel in 2004, additional treatments are available, including abiraterone, which is also administered with prednisone. Therefore, patients are increasingly likely to have prednisone therapy several times throughout their disease course, and the contribution of prednisone to the efficacy of docetaxel is unknown. METHODS: We conducted a retrospective study of patients with mCPRC treated with docetaxel at our institution between 2004–2014. Patients were divided into 2 cohorts based upon whether prednisone was co-administered with docetaxel. Cohorts were further stratified based upon prior prednisone (with abiraterone) or hydrocortisone (with ketoconazole) use. The primary endpoint was clinical/radiographic progression-free survival (PFS). The secondary endpoints were >50% PSA response rate and PSA progression-free survival (PSA-PFS). A multivariable cox regression model was constructed to determine if prednisone use was independently predictive of PFS. RESULTS: We identified 200 consecutive patients for inclusion in the study: 131 men received docetaxel with prednisone and 69 received docetaxel alone. The docetaxel-prednisone cohort had superior PFS compared to the docetaxel-alone cohort (median PFS: 7.8 vs 6.2 months, HR 0.68 [95% CI 0.48–0.97], p=0.03). Prednisone was associated with a reduced risk of progression on docetaxel in the propensity score-weighted multivariable Cox model (p=0.002). Among abiraterone- or ketoconazole-pretreated patients, no difference in PFS was observed between prednisone-containing and non-prednisone containing cohorts (median PFS: 7.1 vs 6.3 months, HR 0.96 [95% CI 0.59–1.57], p=0.87). CONCLUSIONS: The incorporation of prednisone potentially augments the efficacy of docetaxel in patients with mCRPC. We hypothesize that this advantage is limited to patients who have not previously received corticosteroids. Prospective confirmation is needed.