Introduction:

Sipuleucel−T reduced risk of death by 22.5% (P = 0.032) in the IMPACT trial, which excluded men with baseline PSA <5.0 ng/mL. Lower baseline PSA levels are associated with lower disease burden and a greater benefit with sipuleucel-T, with greater benefits in black men. We examined overall survival in sipuleucel-T-treated mCRPC patients with baseline PSA<5.0 ng/mL in PROCEED (NCT01306890).

Methods:

This exploratory analysis included 1,866 men who received 1 or more infusions of sipuleucel-T and had a reported baseline PSA. First, patients were grouped according to baseline PSA < 5.0 ng/mL (low PSA; n = 451 [23.9%]) or ≥ 5.0 ng/mL (high PSA; n = 1435 [76.1%]). Overall survival was calculated per Kaplan-Meier methods. Second, overall survival within these subgroups was analyzed by self-reported race.

Results:

Demographics and baseline characteristics are described in Table 1. Median survival time was 47.9 months (95% CI: 43.8-52.0 months) and 26.4 months (95% CI: 24.7-27.7 months) in the low and high PSA groups, respectively (hazard ratio, 2.12, 95% CI: 1.83-2.46; P < 0.001). In the analysis by race, risk of death was 51% lower in low PSA black men (n = 35) vs white men (n = 407) (hazard ratio, 0.49; 95% CI: 0.26-0.92; P = 0.026) and 20% lower in high PSA black men (n = 185) vs white men (n = 1227) (hazard ratio, 0.80; 95% CI: 0.66-0.97; P = 0.024).

Conclusion:

This post-hoc analysis demonstrates a survival of nearly 4 years when sipuleucel-T treatment is initiated in men with low PSA (<5.0 ng/mL) compared to patients with high PSA. Further, regardless of whether baseline PSA was above or below 5 ng/mL, treatment with sipuleucel-T resulted in a significant reduction in risk of death in black men as compared to white men. Use of sipuleucel-T in men with lower disease burden may improve their survival.

Funding: Dendreon Pharmaceuticals LLC