Why does PSA continue to rise and prostate cancer disease continue to progress (new tumors develop and existing tumors continue to get bigger) when a man has an immune system treatment to go after their prostate cancer? This issue is probably the major marketing hurdle faced by Dendreon’s Provenge and based on the current statistics from the early trials of Prostvac, it will also plague Bavarian Nordic.
I hear again and again from survivors that they have had Provenge and it failed. What they actually mean is that while they took Provenge and during the immediate time after their infusions their PSA still climbed and scans indicated that their disease was progressing. Concluding that the Provenge treatment failed is simply an error in understanding the nature of the treatment.
Conventional prostate cancer treatments like hormonal therapy and chemotherapy are designed to target the tumors and when they work we see a quick lowering of PSA and often a regression of the disease. Thus, men conclude that the treatment works as they see specific evidences of the effect on the tumor and its environment.
Immune therapy (Provenge and investigational treatments like Prostvac) don’t target the tumor. These types of treatments instead target the immune system by building the immune system and making it sensitive to the prostate cancer. Once the immune system has been built up and sensitized to the cancer it will, if successful, attack the tumor and the tumor microenvironment. However, this takes time and it is currently impossible to measure the effectiveness of the treatment at this early stage.
So, what does this actually mean? It is simple. Expect that your PSA will continue to increase and that your scans will be continue to show an increase in disease progression while you get the therapy. Don’t conclude that the treatment does not work, there is no way currently that can tell us if the therapy will work for us.
Be patient and start immune therapy sooner than later, while your PSA is at very low levels. From retrospective analysis of the IMPACT Trial (the phase III trial of Provenge) it is shown that the men who received the most survival benefit from Provenge were the men with the lowest PSA scores when they had the treatment.
I know, it is hard to feel that you are just sitting back and doing nothing while your PSA increases and the scans get worse, but remember that you are most likely contributing to extending your life. Immune therapy is different then conventional therapies, not unlike the difference in side effect profiles. Immune therapy have minimal side effects, conventional toxic therapies have significant side effects, but they all extend life.
Joel T. Nowak, M.A., M.S.W.