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Updated IMPACT: survival benefit for sipuleucel-T upheld in metastatic castration-resistant prostate cancer
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Genitourinary Cancers Symposium
Results from an updated analysis of the IMPACT trial confirmed that patients with metastatic castration-resistant prostate cancer assigned the vaccine sipuleucel-T lived longer than those assigned placebo.
Results from IMPACT, a randomized, double blind, placebo-controlled phase-3 trial released in 2009, demonstrated a survival benefit associated with sipuleucel-T (Provenge, Dendreon), an investigational autologous active cellular immunotherapy for the treatment of prostate cancer.
Patients in the trial were stratified by primary Gleason grade, number of bone metastases and bisphosphonate use and randomly assigned three doses of IV sipuleucel-T (n=341) or placebo (n=171) at two-week intervals.
Philip Kantoff, MD, leader of the Dana-Farber/Harvard Cancer Center prostate cancer program and director of the prostate cancer Specialized Program of Research Excellence, presented updated findings, including OS based on additional events collected prior to study closure, at the 2010 Genitourinary Cancers Symposium. He said sipuleucel-T represented a “new paradigm” as the first drug to show an improvement in OS in metastatic castration-resistant prostate cancer.
“The treatment effect appeared to be consistent across multiple patient subsets based on baseline characteristics,” he said.
This new analysis was conducted after 349 deaths and an estimated median follow-up time of 36.5 months. Kantoff said the updated analysis again showed a survival benefit associated with sipuleucel-T using the primary model (HR=0.759) or unadjusted Cox model and log rank test (HR=0.759; 95% CI, 0.606-0.951). Median survival of 25.8 months in the sipuleucel-T group and 21.7 months in the placebo group, and 36-month survival probability of 32.1% for sipuleucel-T and 23% for placebo remained unchanged.
Sipuleucel-T was more commonly associated with chills, pyrexia, headache, influenza-like illness, myalgia, hypertension, hyperhidrosis and groin pain than in the placebo group. Kantoff said the majority of these events were grade-1/grade-2 and resolved within a few days. – by Jason Harris
For more information:
- Kantoff P. #8. Presented at: the 2010 Genitourinary Cancers Symposium; March 5-7, 2010; San Francisco.
If sipuleucel-T improves overall survival, which it has now been shown to do, everybody who has metastatic prostate cancer should try to get that agent. It's the first immunologic agent in PC that's been shown to have a survival advantage. It's a very big deal.
- Nicholas J. Vogelzgang, MD
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