A brief discussion on how selection of imaging should be approached for patients receiving androgen deprivation therapy (ADT) for prostate cancer.
Brian Helfand, MD, PhD: In the example I talked about, we discussed that the patient received hormone therapy. That becomes interesting because we don’t know the impact of hormones on the expression of the amino-based transporter, like the fluciclovine based may use, or on the expression of PSMA [prostate-specific membrane antigen], which is what the PSMA PET [positron emission tomography] scans use. There have been studies in this space, and the fluciclovine-based studies suggest that it tends to be androgen independent. This means that even if men have received hormone therapy, the performance of fluciclovine appears to be similar to men who have never received hormone therapy. If a patient has been on hormone therapy for a long time, I feel comfortable that a fluciclovine scan will give us our answer.
There has been some controversy over PSMA. That’s not surprising because PSMA expression is influenced by hormones. Normal testosterone can ramp up the PSMA expression, but hormone therapy, depending on where that cell is, can increase or decrease it. Some of the studies in Gallium PSMA-based imaging and the F18 PSMA scans have suggested that there may be differences in the ability of PSMA to detect among patients who are on hormone or who have hormone-refractory disease. This is an ongoing investigation, but we should pay attention to it and consider it.
If all you have at your institution is a PSMA-based scan, it’s not inappropriate to obtain that scan and to see what it shows. If that continually comes back negative, you should consider modalities [that are] fluciclovine based to explore and see if there are differences. At my institution, we’ve used both modalities in the same patient, when 1 was negative and the other was positive. It’s an ongoing target. That’s an active area of research interest—to define when we use what scan. But in a practical nature, use the imaging modality that’s available and easiest to obtain right out of the gate.
Transcript edited for clarity.