Imaging Prostate Cancer
Posted: Nov 01, 2018
POSTED: September 04, 2015
Prostate Forum recently spoke with Dr. Paul Schellhammer, a urologic oncologist who has been involved in key clinical trials for the treatment of prostate cancer, including studies that led to Provenge’s FDA approval. He has served as President of the American Urologic Association, Chair of the Department of Urology at Eastern Virginia Medical School, and has also been on the editorial boards of several journals. These experiences undoubtedly give him a broad view of prostate cancer and its treatments. Prostate Forum recently spoke with him about Provenge, new frontiers in immunotherapy, Estrogen use, Active Surveillance, and PSA screening.
You can read the entire conversation in Prostate Forum Volume 15 # 9.
Prostate Forum asked: Provenge was the first cancer vaccine to obtain FDA approval. How do you see Provenge fitting into the treatment of advanced prostate cancer now that we have a number of other drugs like Xtandi, Zytiga, and Xofigo? When would you use Provenge? Which patients are most likely to benefit from Provenge?
Dr. Shellhammer said: Through our practice, I’ve had the opportunity to participate in a number of clinical trials. Provenge came to our attention in 1999 when immunotherapy was barely on the horizon. There was really nothing beyond androgen deprivation at the time for the treatment of metastatic prostate cancer. Provenge was a leap of faith. For ten years, we enrolled a large proportion of patients in the trials, which on completion materialized into what I see as a win-a survival benefit-but the trial outcomes have been very controversial.
Provenge presents a problematic discussion for physicians to have with patients. If treatments are selected based on achieving a best initial response, then the drift is away from Provenge because the initial response regarding PSA level is not comparable to the PSA response obtained from other agents. PSA does not drop abruptly after Provenge.
Provenge has a unique mechanism of action. The immune system is a potent force that will be harnessed ever more in the future to combat cancer because it is flexible, adaptable, durable, and dynamic. It fits all the qualifications for accommodating to the changes a malignant cell undergoes to survive-the Darwinian principle.
Provenge bolsters a patient’s immune biological bank with an outcome that is recognized as valid-that is survival, extension of life. And in the best Level 1 evidence trials, Provenge has been shown to increase survival by 4+ months. (This is similar to enzalutamide and abiraterone, which extend life in the 4-month range.)
Provenge is a therapy that has a totally different mechanism. It is done quickly over a month. It has a favorable side effect profile. But patients should recognize that they are going to go on to other therapies. Just as if chemotherapy regimen number 1 doesn’t work as well as the doctor thinks it should-or it works for a while and then stops: a patient will go on to protocols 2 or even 3. I think Provenge is best offered prior to other treatments, because that is when the volume of disease is lowest and the immune system is least compromised. The patient receives Provenge and then proceeds to other therapies as required.
What do I mean by ‘as required’? How do we know a patient will need another treatment after Provenge? There might be worsening of the bone scan or PSA progression may accelerate. Even though I discuss PSA as being an important and visible issue, medical oncologists and urologic oncologists recognize PSA and survival don’t march in lockstep.
Therefore, the fact that the PSA doesn’t go down abruptly after Provenge doesn’t mean the therapy isn’t providing a benefit. We know that the PSA is not an index of survival, though it may be an index of disease activity at the time.
How physicians present Provenge makes a difference. Some just don’t feel it is appropriate, despite the fact that it has met the bar of level I evidence through randomized controlled trials. I have received Provenge and have been satisfied with the decision and results.
Prostate Forum asked: What do you think about the current trend to abandon prostate cancer screening? What do you think will be the consequences of the move away from screening?
Dr. Schellhammer: The worst-case scenario is that we’d go back to what I remember as a urology resident: hospital beds occupied by men with extensive bone metastases and debilitating pain.
In the current age, I do not believe we would allow a cancer to get to that point. But bone metastases will become much more common and, of course, once the cancer involves bone, lethal events have been put into motion.
I think we need wise use of PSA testing: not testing octogenarians, not testing men with co-morbidities, not testing repetitively year in and year out, and risk-adapting. However, making these decisions wisely is difficult and time-consuming for me—and all I do and think about is prostate cancer. The vast majority of the patients I care for have prostate cancer. For a primary care physician, who carries the burden of treating many diseases, it is far easier, and now much safer, to just follow the US Preventative Task Force’s recommendations.
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