Prostate Cancer Imaging: Unmet Needs and Knowledge Gaps

Medical oncologist Tian Zhang, MD, outlines the remaining unmet needs and knowledge gaps surrounding imaging of prostate cancer.


Alan Bryce, MD: Dr Zhang, what about unmet needs or knowledge gaps in this space? There are a lot of knowledge gaps with a new technology, but what comes to mind?

Tian Zhang, MD, MHS: Sure. [Declan] Murphy, [MBBCh,]at ASCO GU [American Society of Clinical Oncology Genitourinary Cancers Symposium] had a nice slide that pointed out, are we historic imagers, are we novel imagers? Using PSMA PET [prostate-specific membrane antigen positron emission tomography] allows us more accurate diagnosis, and we’re able to pinpoint disease. But how much of that information are we using today to confer our treatment selection, and also in terms of helping our patients understand what is needing to be treated, and what we would not have seen in the past? Our prior trials were all based on conventional imaging. I think that gap is an unmet need and an opportunity. In PSMA-positive disease, there are patients in the localized high-risk setting who are going to have some evidence of metastatic spread, whether that’s nodal or to a bone, but that is not clearly apparent on our conventional imaging. Those patients may be intensified with systemic treatment, and that’s not wrong in our current landscape. We can see that there’s metastatic disease. But how many of those patients are overtreated by adding that systemic treatment? I don’t think we know that answer.

The other possibility is that in our potentially oligometastatic disease by conventional imaging, those patients may be upstaged further by showing more sites of disease, so higher disease burden. If we were going to consider metastasis-directed therapy or treatment of the prostate bed for those in the salvage setting, and we skipped those treatments that potentially have life-prolonging benefit, then perhaps we are undertreating a portion of patients. There are gaps in what we know right now and how we practice for our patients. Hopefully, we are all being careful in trial design in order to show in prospective studies how to best treat these patients going forward.

Alan Bryce, MD: Absolutely. One of the things I always try to emphasize with my patients is to say the imaging does not change the biology. It shows us what the disease is doing more clearly, but the disease was doing this whether we imaged it or not. The imaging isn’t changing the outcome, it’s just giving us more information by which to make our decisions. I think Dr Lowentritt’s point is one of the important ones of not overcalling disease. There are false positives, so we never want to deny a patient a chance at cure by overcalling a false positive on a scan. That’s probably the part I worry about most. I don’t worry so much about 19 metastases vs 17, conventional imaging vs PSMA, but it’s the patient who we label as incurable, that’s the one I worry about. That’s probably the biggest point of caution I would emphasize for the audience.

Transcript edited for clarity.

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