No survival benefit found after extended treatment with docetaxel for patients with castration‐resistant prostate cancer

BACKGROUND: Docetaxel (DOC) has been widely accepted as a therapeutic option for castration-resistant prostate cancer (CRPC). Evidence-based clinical guidelines have stipulated its use up to 10 cycles in most health care systems. There has been a paucity of information regarding potential benefits of its use over 10 cycles. The purpose of this study is to re-examine the rationale for the clinical guidelines concerning cycles of DOC in CRPC. METHODS: Between July 2007 and July 2016, a total of 122 CRPC patients received at least five cycles of DOC at Jikei University and its affiliate hospitals. Doses of DOC (75 mg/m 2 ) were administered every 3 to 4 weeks. Clinical outcomes between patients receiving extended cycles of DOC (≥11 cycles, extended [ex]-DOC group) were compared to those receiving fewer (≤10 cycles, short-DOC group). A subgroup of patients who had discontinued DOC owing to adverse events, but whose disease did not progress, were also considered for comparison (adverse events [AE] group). Overall survival from the induction of DOC was the primary outcome measure. Univariate and multivariate analyses were conducted to analyze variables associated with overall survival. RESULTS: The ex- and short-DOC groups included 80 and 42 patients, respectively. Most baseline demographics did not differ between groups. However, in the short-DOC group more patients had received abiraterone acetate and/or enzalutamide before chemotherapy, age at DOC induction was younger, and lactate dehydrogenase at DOC induction was higher. Overall survival was significantly longer in the ex-DOC group compared to the short-DOC group (median, 53 and 27 months, respectively; P = .04). A subgroup of 22 patients in AE group was compared to compensate for potential bias. Overall survival from the induction of DOC was comparable between AE group and ex-DOC groups (median, 53 vs 53 months, respectively; P = 0.87). Univariate and multivariate analyses did not show any advantage of extended use of DOC on patient survival. CONCLUSIONS: The results of this study failed to show the survival benefit of extended use of DOC over 10 cycles in CRPC patients in the era of innovative drugs such as abiraterone acetate, enzalutamide, and cabazitaxel. Further prospective studies are required to confirm our findings.