Survival Outcomes of Sipuleucel-T Phase III Studies: Impact of Control-Arm Cross-Over to Salvage Immunotherapy.

Published

Journal Article

Sipuleucel-T is an autologous cellular immunotherapy for asymptomatic/minimally symptomatic metastatic castrate-resistant prostate cancer (CRPC). After disease progression, control-arm patients on three double-blind, randomized phase III sipuleucel-T trials were offered, in nonrandomized open-label protocols, APC8015F, an autologous immunotherapy made from cells cryopreserved at the time of control manufacture. These exploratory analyses evaluated potential effects on survival outcomes associated with such treatment. Of 249 control-treated patients, 165 (66.3%) received APC8015F. We explored the effects of APC8015F on the overall survival (OS; Cox regression) of control-arm patients and treatment effects of sipuleucel-T versus control adjusted for APC8015F treatment [iterative parameter estimation model (IPE)]. The median time to first APC8015F infusion was 5.2 months (range, 1.8-33.1) after randomization and 2.2 months (0.5-14.6) after progression. After disease progression, median survival was longer for APC8015F-treated versus control-only treated patients [20.0 vs. 9.8 months; HR, 0.53; 95% confidence interval (CI), 0.38-0.74; P < 0.001]; however, baseline characteristics were more favorable for APC8015F-treated patients. Multivariate regression analyses identified lactate dehydrogenase, alkaline phosphatase, hemoglobin, ECOG status, age, and number of bone metastases as potential (P < 0.1) independent predictors of postprogression survival. After adjusting for these predictors, APC8015F (HR, 0.78; 95% CI, 0.54-1.11; P = 0.17) treatment trended toward improved survival. Estimated median OS benefit for sipuleucel-T versus control adjusted for APC8015F treatment was 3.9 months if APC8015F had no effect and was 8.1 months if APC8015F was equally as effective as sipuleucel-T. Exploratory analyses indicate that APC8015F treatment may have extended patient survival, suggesting the sipuleucel-T OS advantage in CRPC may be more robust than previously estimated.

Full Text

Duke Authors

Cited Authors

  • George, DJ; Nabhan, C; DeVries, T; Whitmore, JB; Gomella, LG

Published Date

  • September 2015

Published In

Volume / Issue

  • 3 / 9

Start / End Page

  • 1063 - 1069

PubMed ID

  • 25943532

Pubmed Central ID

  • 25943532

Electronic International Standard Serial Number (EISSN)

  • 2326-6074

International Standard Serial Number (ISSN)

  • 2326-6066

Digital Object Identifier (DOI)

  • 10.1158/2326-6066.cir-15-0006

Language

  • eng