1792P Effects of enzalutamide on overall survival +/- early docetaxel in participants aged less than 70 yrs versus greater than or equal to 70 yrs in ENZAMET (ANZUP 1304)

Enzalutamide (ENZA) and abiraterone are standard of care for people with metastatic hormone-sensitive prostate cancer (mHSPC). It is important to understand the benefits of these agents in older patients, who may be more frail and have more co-morbidities. In this post-hoc analysis, we assessed the efficacy of ENZA in patients with mHSPC ≥70yrs vs <70yrs of age. ENZAMET randomly assigned participants (pts) with mHSPC to treatment with testosterone suppression (TS) plus either a non-steroidal anti-androgen (NSAA) or enzalutamide (ENZA). Stratification factors included age, volume of disease (high vs low), and planned use of concurrent docetaxel (DTX) as agreed by the participant and the treating physician. The same methods were used for overall survival (OS) analysis as in the full trial. Quality of Life (QoL) and safety analyses by age ≥70yrs vs <70yrs are ongoing. Of 1125 pts randomised, 514/1125 (46%) were aged ≥70yrs. The rate of DTX usage was lower in pts aged ≥70yrs (35% vs 52%). The beneficial effects of ENZA on OS seen in the whole cohort are maintained in pts aged ≥70yrs, regardless of planned use of early DTX (Table). Pts aged ≥70yrs treated with ENZA had a significant improvement in OS (Table) in line with younger pts. Table: 1792PHazard ratios (HR) and confidence intervals (CI) for effects of ENZA vs NSAA on OS in subgroups according to age and planned DTXCharacteristicNDeathsHR95% CIFull cohort11254760.700.58-0.84Age alone<70yrs All6112390.750.58-0.97≥70yrs All5142370.640.50-0.83Age and DTX<70yrs and DTX3221470.870.63-1.20≥70yrs and DTX181840.730.47-1.12<70yrs and No DTX289920.620.41-0.94≥70 and No DTX3331530.600.44-0.83 Open table in a new tab This post-hoc analysis demonstrates that pts aged ≥70 yrs treated with ENZA/TS +/- DTX have similar benefical treatment effects to the overall cohort. These data suggest ENZA is a suitable option for older men with mHSPC fit for enzalutamide.