Medical OncologyLower Baseline Prostate-specific Antigen Is Associated With a Greater Overall Survival Benefit From Sipuleucel-T in the Immunotherapy for Prostate Adenocarcinoma Treatment (IMPACT) Trial
Section snippets
Study Design
The study design and patient inclusion have been previously described in detail.3 The trial enrolled patients with mCRPC. Initially, only men with asymptomatic disease, a Gleason score of ≤7, and PSA of ≥5 ng/mL were enrolled. The trial was subsequently amended to include men with any Gleason score and minimally symptomatic disease. Patients with ECOG PS of ≥2, visceral metastases, or previous treatment with >2 chemotherapy regimens were excluded.3 Further details of the trial are registered at
Patients
Patients in the study population had a median age of 71 years, and approximately 82% of enrolled patients were chemotherapy-naive.3 Baseline clinical characteristics for the prognostic factors previously identified as important in this patient population were similar in the 2 study groups.3
Prognostic Factors and Efficacy by Prognostic Subgroup
All of the variables identified by Halabi et al6 and available for evaluation in IMPACT (PSA, LDH, Hgb, ECOG PS, ALP, and Gleason score) were significant independent prognostic factors for survival (P <.05)
Comment
We have previously demonstrated that sipuleucel-T prolongs survival in men with mCRPC and is effective in multiple patient subgroups. In this exploratory analysis, we show a trend toward a more pronounced treatment effect in patients with better baseline prognostic features. This appeared most prominent with baseline PSA, where those in the lowest quartile (<22.1 ng/mL) achieved a 49% reduction in the risk of death (HR, 0.51; 95% CI, 0.31-0.85) and a median survival difference of 13.0 months
Conclusions
The results from our exploratory analyses suggest that the greatest magnitude of benefit with sipuleucel-T treatment was observed among patients with better baseline prognostic factors and particularly those with lower baseline PSA values. These findings provide a rationale for immunotherapy as an early step in sequencing treatment algorithms for mCRPC and also suggest a greater benefit when immunotherapy is used earlier in the treatment paradigm.
Acknowledgments
Medical writing assistance was provided by Emma Warr and Stuart Langley of Gardiner-Caldwell Communications and funded by Dendreon Corporation.
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Financial Disclosure: James B. Whitmore, Robert Sims, and Mark W. Frohlich are employees of Dendreon Corporation. Paul F. Schellhammer is on the advisory board and speakers bureau for Dendreon Corporation and on the advisory board for Janssen. Gerald Chodak is a consultant for Dendreon Corporation and Watson and is a speaker for Dendreon Corporation, Amgen, and Watson. Philip W. Kantoff is on the advisory boards for Dendreon Corporation, Bavarian Nordic Immunotherapeutics, Bellicum, Sanofi, Janssen, Bristol Myers Squibb, BIND, and Pfizer.
Funding Support: This study was funded by Dendreon Corporation.