Cancer ABCs has been an early and consistent believer in the efficacy of the immunotherapy treatment Provenge for men with prostate cancer. We have stated many times that Provenge is effective because it extends a man’s life. We know this because three different phase III clinical trials have demonstrated that when Provenge is used according to its label (for men who are castrate resistant) men live longer than those who do not use Provenge.
We also know that the evidence clearly shows us that once a man becomes castrate resistant, as per the FDA approved label, the earlier a man has Provenge, the more likely he is to experience the advantages of Provenge, a longer survival.
The understanding that the earlier Provenge is used in castrate resistant men with prostate cancer has led many men to ask why not use Provenge even earlier when they are still castrate sensitive? This question is an excellent one which follows the logical next step; however, the answer is surprising!
The surprising answer is that in a randomized, double-blind, controlled trial to determine Provenge’s biologic activity in men with castrate sensitive prostate cancer following a prostatectomy and 3 to 4 months of hormone therapy, those men who did receive Provenge did not get any benefit when their time to experiencing a biochemical failure (BF), or their having a PSA relapse was evaluated.
The researchers concluded that there was no significant difference in time to BF between the two trial groups, those who received Provenge while still being castrate sensitive vs. those who did not have Provenge.
They did find that in those men who did receive Provenge their PSA doubling time (PSADT) did increase which can be interpreted as a possible positive prognostic sign. PSA kinetics in general and PSADT specifically has been shown to be a robust predictor of prostate cancer-related mortality. Despite this, PSADT is not a validated endpoint for clinical trials, and to date, no studies have examined the link between treatment-induced alteration in PSADT and time to disease progression or death.
Long-term follow-up will be necessary to determine if clinically important events, such as distant failure, are affected by therapy as well as overall survival.
In other words, we do not have any compelling evidence that taking Provenge while a man is still castrate sensitive can have any effect on their overall survival.
Clinical Cancer Res; 17(13); 4558–67. ©2011 AACR.
Cancer ABCs does want to disclose that they have received economic support from Dendreon, the company that manufactures Provenge. We also want to point out that Dendreon did pay to support the research cited in this post.
By Joel T Nowak, MA, MSW