pTVG-HP DNA vaccine in PSA-recurrent prostate cancer: median survival 13.4 vs 8.6 years in long-term analysis of a randomized phase 2 trial

In a randomized phase 2 trial (NCT01341652), the pTVG-HP DNA vaccine encoding prostatic acid phosphatase was associated with a median overall survival of 13.4 years versus 8.6 years with placebo (48 vs 49 patients, HR 0.42; 95% CI, 0.20-0.90) in men with PSA-recurrent, non-metastatic, non-castrate prostate cancer, at a median follow-up of 4.1 years. Median time to starting androgen deprivation therapy (2.2 vs 1.4 years) and time to the next therapy after starting it (4.7 vs 2.1 years) were also longer, and in a 59-patient single-site subgroup the adjusted HR was 0.60 (95% CI, 0.36-1.00). Key caveat: the trial's primary endpoint — 2-year metastasis-free survival — did NOT differ between arms, and the survival analysis is a long-term assessment added after the trial was reopened, in a small sample and with wide confidence intervals. The authors read this as a signal that cancer vaccines may act on longer-term endpoints that short follow-up misses; confirmation requires a phase 3 trial.