Update on PROSPECT: Phase III Trial of Prostate Cancer Vaccine
Posted: Friday, August 3, 2018
The prostate cancer vaccine PROSTVAC did not improve clinical outcomes, according to the double-blind, randomized phase III trial PROSPECT. The trial failed to confirm the results of the previous phase II trial, in which the vaccine had improved overall survival by 8.5 months, from 16.6 months to 25.1 months. The updated findings were presented atthe 2018 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract 5006) byJames Gulley, MD, PhD, FACP,of the National Cancer Institute, and colleagues.
“There was no improvement in survival for men treated with the vaccine or the vaccine with GM-CSF over placebo,” Dr. Gulley told Cancer Therapy Advisor. Nor was there any difference in the risk of disease progression at 6 months, “so, clearly here there was no difference in clinical outcomes.”
The trial enrolled 1,297 patients in 15 countries (with an average age of 71) who had asymptomatic or minimally symptomatic metastatic, castration-resistant prostate cancer. Patients were assigned to one of three trial arms: vaccine, vaccine with granulocyte macrophage colony-stimulating factor (GM-CSF), or placebo.
The primary endpoint, overall survival, was 34.8 months for the vaccine arm, 33.9 months for the vaccine with GM-CSF arm, and 34.7 months for the placebo arm. The vaccine also conveyed no benefit in the secondary endpoint, “alive without event at 6 months.” The authors noted that all of the overall survival results were about 1 year longer than expected when enrollment began in 2011, which they suggest is due to an improved standard of care.