SUO 2017: Survival Outcomes For African-American Versus Matched Caucasian Patients With mCRPC Treated With Sipuleucel-T

Washington, DC ( It is known that prostate cancer risk and mortality is higher in African American (AA) men versus Caucasian (CAU) men. In an analysis of three phase 3 mCRPC trials, AA patients appear to derive greater survival benefit with sipuleucel-T, an autologous cellular immunotherapy for asymptomatic/minimally symptomatic mCRPC. AA patients on sipuleucel-T had a 30.7-month median overall survival (OS) benefit versus control (AUA 2012 P953), in contrast to a 4.1-month OS benefit with sipuleucel-T versus control for all pts in IMPACT (NEJM 2010;363:411). As the prior analysis did not adjust for baseline differences between races, The authors matched AA to CAU pts on sipuleucel-T to better assess racial differences in sipuleucel-T benefit and cumulative antigen presenting cell (APC) activation, which correlates with OS.

Methods: Data from phase 3 mCRPC trials that randomized patients 2:1 to sipuleucel-T or control (D9901
[NCT00005947]; D9902A [NCT01133704]; IMPACT [NCT00065442]) were analyzed. Thirty-three AA sipuleucel-T patients were matched with 66 CAU sipuleucel-T patients based on predicted Halabi survival.

Results: Median follow-up was 36 (CAU) and 33.7 (AA) months. AA patients on sipuleucel-T had a 20.6-month longer median OS (45.3 months; 95% CI 23.4–NE) versus CAU patients (24.7 months; 95% CI 18.1–29.4) (HR=0.49; 95% CI 0.26–0.91; p=0.02). Median event-free survival (time to death or anticancer intervention [ACI]) was 10.7 months for AA patients (95% CI
8.5–21.5) versus 8.7 months for CAU patients (95% CI 6.6–11.5) (HR=0.74; 95% CI 0.47–1.18; p=0.20). Median time to next ACI was 23.5 months in AA patients (95% CI 9.4–NE) versus 16.3 months in CAU patients (95% CI 9.7–25.6) (HR=0.78; 95% CI 0.42–1.43; p=0.42). In AA patients, median APC activation was higher with sipuleucel-T infusion 1 versus CAU patients (7.0 versus 5.5, p=0.004). Median (range) cumulative APC activation over the three infusions was 27.7 (2.9–60.4, AA) versus 25.7 (4.3–46.4, CAU) (p=0.083).

Conclusion: Prior studies found sipuleucel-T provides OS benefit to both AA and CAU mCRPC patients. This study shows that AA men treated with sipuleucel-T had longer survival, suggesting sipuleucel-T may provide greater OS benefit in AA. The basis for this may be biologic (greater APC activation). Obviously, additional studies with larger sample sizes are needed to confirm this finding.

Presented by: Stephen J. Freedland, Cedars Sinai Medical Center

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, @GoldbergHanan, at the 18th Annual Meeting of the Society of Urologic Oncology, November 29-December 1, 2017 – Washington, DC