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Prostate cancer vaccine improved survival in hormone-refractory disease
Survival was 34% for those treated with the vaccine compared with 11% for those taking placebo.
Men with advanced and often untreatable prostate cancer who received a therapeutic cancer vaccine survived longer than those who received a placebo, according to a recent study. The vaccine group lived an average of 4.5 months longer and had a greater than threefold increase in survival at 36 months, compared with patients in the placebo group.
Researchers conducted a double-blind, placebo-controlled, phase-3 trial to test the efficacy of the vaccine, called sipuleucel-T (Provenge, Dendreon), in delaying disease progression and prolonging survival in patients with asymptomatic metastatic hormone refractory prostate cancer.
The vaccine was well-tolerated by patients, according to the study. The most common adverse events, including fever and chills, were typically mild.
Eric J. Small, MD, professor of medicine and urology at the University of California, San Francisco, led the study in collaboration with 19 institutions in the United States.
“This trial is an important milestone in the development of new treatments for prostate cancer patients,” said Small in a prepared statement. “The potential survival benefit that was observed may offer important benefits to patients and would represent the first time that immunotherapy has provided a survival advantage in prostate cancer.”
Sipuleucel-T is an investigational immunotherapy vaccine designed to stimulate T-cell immunity to prostatic acid phosphatase, an antigen found in about 95% of prostate cancers but not in nonprostate tissue.
A total of 127 patients with asymptomatic metastatic hormone-refractory prostate cancer received three transfusions of sipuleucel-T or placebo every two weeks. Of this group, 115 patients had progressive disease at the time of data analysis and all patients were followed for survival for 36 months.
The median overall survival was 25.9 months for sipuleucel-T-treated patients and 21.4 months for placebo-treated patients, according to the study. After three years, survival was 34% for those treated with the vaccine, compared with 11% for those taking the placebo.
The trial did not meet its primary endpoint of demonstrating a statistically significant difference in progression of the disease from diagnosis, according to the study results that appeared in the Journal of Clinical Oncology.
“We found that the time to disease progression for sipuleucel-T was 11.7 weeks compared with 10 weeks for placebo,” he said. “This shows the difficulties in using the worsening of the disease as an intermediate marker for overall survival of patients treated with immunotherapy. The study however, suggests that sipuleucel-T may provide a survival advantage to asymptomatic hormone-refractory prostate cancer patients.”
Dendreon sponsored the trial.
Editor’s note: This study is very encouraging and suggests that immune modulation may play a role in the management of men with prostate cancer. The study rationale was sound and the results provocative. However, caution is indicated. The primary endpoint (progression delay) was not met and the survival endpoint is a secondary one. The trial is small and this small size limits the conclusions which can be drawn. This result is intriguing - and merits a larger trial, of sufficient size to robustly address the survival endpoint. – Donald L. Trump, MD, FACP
For more information:
- Small EJ, Schellhammer PF, Higano CS, et al. Placebo-controlled phase III trial of immunologic therapy with sipuleucel-T (APC8015) in patients with metastatic, asymptomatic hormone refractory prostate cancer. J Clin Oncol. 2006;24:3089-3094.