Prostate Cancer Coverage from Every Angle

Tanya Dorff, MD, on Androgen Deprivation, External-Beam Radiation Therapy, and Oligometastatic Hormone-Sensitive Prostate Cancer

Posted: Thursday, September 1, 2022

Tanya Dorff, MD, of City of Hope, discusses the challenges posed when treating patients with oligometastatic prostate cancer, for whom lifelong intensive therapy may not be appropriate. Dr. Dorff reviews several recent studies, the need for the most sensitive imaging tools, and the complex treatment landscape that makes it more important than ever to enroll patients in clinical trials that may help better define best practices.


Disclaimer: This video transcript has not been proofread or edited and may contain errors.

Oligometastatic prostate cancer poses some significant challenges. We know from the STAMPEDE trial that treatment of the prostate primary can yield important benefits in men who are diagnosed with de novo metastatic disease and have a low volume of metastases. But when we think about oligometastatic patients, we're also thinking about patients who relapse following definitive management to the prostate primary earlier, and who have just one to five, or sometimes one to three, metastases detected on imaging. These men don't fit as easily into a paradigm of lifelong intensified therapy, which is, of course, how we're treating most of our metastatic prostate cancer patients. Oligometastatic prostate cancer patients have been enrolled on those trials of upfront intensified systemic therapy, but they've also been treated on trials of no androgen deprivation and only stereotactic radiation. So, these are trials such as ORIOLE, POPSTAR and STOMP. So, first and foremost, the definition of oligometastatic prostate cancer is reliant on imaging. And so, it makes sense that we would have more success, if we want to use metastasis directed therapy, if we can use our most sensitive imaging to locate the metastases. So, this typically would involve a PSMA PET scan or perhaps Fluciclovine PET scan. Using conventional imaging, such as CTs and bone scans, would be likely to underestimate where the disease is and would, therefore, likely result in a lower success rate. In ORIOLE, one of the trials that tested metastasis directed therapy without androgen deprivation, 48% of patients were free of androgen deprivation at two years. In another trial, STOMP, the median ADT free survival was 21 months, although this is not a firm endpoint. The observation group, for instance, who received no treatment, had an ADT free survival of 13 months. The recent TROD trial, which selected patients based on PSMA pet, found that only 65% had their PSA decreased by 25% or greater. So, clearly even with our best imaging, we are missing some areas of disease. Patterns of failure are typically shown to be outside the areas that we treat with the stereotactic radiation. And so, the question of using androgen deprivation makes sense potentially as a way to treat the micro metastases that are not detectable by imaging. And since ADT added to radiation has improved outcomes in many other scenarios, such as the salvage setting when we're using prostate bed and/or pelvic radiation, it makes sense to combine them here for all of the metastatic patients, as well. But we have very few datasets studying this combination in this setting. Duration of ADT intensity remain open questions, as well. And patient selection factors may be very important, since there are those who could achieve long-term control without androgen deprivation as we saw in STOMP and ORIOLE and those other trials, and men may obviously prefer not to be exposed to ADT. So, this is a complex landscape and enrolling patients on clinical trials whenever possible is going to be really important to help us better define how to best treat these patients.

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