Targeting PSMA in Advanced Prostate Cancer - Episode 6

PSMA-Imaging as a Noninvasive Detection of Metastasis

April 13, 2021
Ulka Vaishampayan, MD

,
Oliver Sartor, MD

Oliver Sartor, MD, and Ulka Vaishampayan, MD, discuss noninvasive imaging with PSMA PET/CT for patients with advanced prostate cancer.

Oliver Sartor, MD: I’d like you to comment a little more about PSMA [prostate-specific membrane antigen], not just in late-disease setting as a predictive biomarker for PSMA therapy but also the imaging in early stage disease and the ability to alter therapy as a consequence of finding metastatic disease when a CT scan and bone scan are probably going to be negative. Would you be able to comment on that and on the recurrent disease setting, when the PSMA may be rising after radical prostatectomy and radiation?

Ulka N. Vaishampayan, MD: This is definitely a great noninvasive way for early detection of metastases. What that allows us to do is detect minimal amounts of metastases with very high sensitivity and specificity with the gallium-68 PSMA PET [positron emission tomography] scan. That has opened new avenues of therapy where you can do local therapy, such as stereotactic body radiation therapy [SBRT], to those specific areas. Oligometastatic disease especially has evolved as a condition with 3 or fewer sites of metastases, where you can do just radiation or local therapy to those lesions and continue to monitor the patients. 

The big advantage of this may be down the road. Because this is a relatively newer condition, we don’t have years and years of follow-up to tell us if this is the right approach and if this improves life expectancy of the patients. It does allow us to delay the systemic therapies, such as androgen deprivation therapy [ADT], which has the possibility of immediate adverse effects like hot flashes and fatigue but also long-term bone loss, increased risk of dementia, cardiac issues, and things like that. This makes it much easier to avoid or at least delay androgen deprivation therapy. 

Oliver Sartor, MD: I wonder if you might want to briefly mention the ORIOLE trial as a specific example of clinical benefit in the treatment of oligometastatic disease. Not everybody is aware of ORIOLE, but it’s really interesting, so maybe you could give a brief landscape of the trial.

Ulka N. Vaishampayan, MD: Both ORIOLE and STOMP trials have randomized patients to do early detection of metastatic disease using novel imaging techniques, such as the PSMA PET scans. Outpatients who were randomized are then selected to receive either standard androgen deprivation therapy, stereotactic body radiation therapy, or local modalities of therapy. So far, there appears to be a clinical benefit, but follow-up is ongoing in both trials. Oliver, do you have anything to add?

Oliver Sartor, MD: We have a lot more to learn when it comes to the utility of these metastasis-directed therapies. The STOMP and ORIOLE trials were conducted in castrate-sensitive oligometastatic disease. We have a whole world of castrate-resistant metastatic diseases that needs to be evaluated. We also need longer-term follow-up. We need to better understand the combination therapies with maybe combining things like abiraterone, enzalutamide, ADT, plus the SBRT and what’s an optimal approach.

We’re in the infancy of these studies, and we’re going to be seeing these studies evolve in rapid-fire fashion over the next 5 to 10 years. This is going to be a growth area because of the better imaging we have, particularly with PSMA PET.

This transcript is edited for clarity.