A Summary of Recent Advances and Remaining Unmet Needs in Targeted Prostate Cancer Imaging

Transcript:

David Albala, MD: We’ve seen in the pathology, and it’s evolving in all different subspecialties. Gerry, we’re running out of time. Can you summarize for me what you think are the unmet needs and clinical challenges surrounding imaging for prostate cancer patients? Are there any emerging data that you’re particularly excited about? You might talk about PSMA [prostate-specific membrane antigen] targeted therapies in the future. What is getting you excited about this topic and this imaging going forward?

Gerald Andriole, MD: PSMA-based therapeutics are obviously very exciting; they must be, it has to be redefined in very specific populations of patients with a slightly longer follow-up. That comes [from] the use of PET [positron emission tomography] scans for biochemical recurrence. Even for staging, will the patient survive longer? Ashley mentioned the EMPIRE-1 study [NCT01666808 ], which did show improved biochemical recurrence after FACBC-based radiation therapy. [That] doesn’t necessarily translate into survival, [but] we’re going to find out [if it does] over the years. That’s a very important thing. In regard to staging, and I think Ashley and Gary also referred to this earlier, is this going to be the Will Rogers phenomenon where we just do a better job categorizing the patient? But in the end, the outcomes are overall the same for the entire group even though individual patients may seem to do better. Those studies are ongoing and they’re waiting. The one thing that I think we’re going to be doing more of in prostate cancer is focal therapy and focal ablation. I wonder how we can integrate PSMA PET/MRI [magnetic resonance imaging] vs PSMA PET/CT [computerized tomography] into planning [and] monitoring the success of a focal ablation. Maybe that’s an open-ended question for Gary. I don’t know the data—if one was to look at patients, the ideal patient for focal therapy right now [has] an MRI target, [if] the targeted biopsies show cancer, [or] the systematic biopsies are negative. In a patient like that, if you also got a PSMA PET scan, would it show other satellite lesions or would it show a larger lesion or a smaller lesion than the MRI did? These are the kinds of things [in which] we’re going to need to do a better job with focal therapy. That’s my final comment; I’ll turn it over to Gary.

Gary Ulaner, MD, PhD, FACNM: I think you summarized it by saying the data is not out there yet. I don’t think I have an answer for you. I would be wary about making size measurements on PET. I don’t think PET is ever going to tell us that the lesion is getting bigger or smaller; depending upon how you window the PET scan, the PET signal looks larger or smaller. So size is not as valuable [of a] component [in] a PET scan as [it is] on your CT or your [MRI]. But certainly, finding additional lesions would be a role of the PET scan. I look forward to the continuing and growing literature that is found [on] PSMA PET and how its value is going to contribute to the care of our patients.

I wish everyone had the ability to have access to all of these agents. I hope that it will be that way as soon as possible. I would draw an analogy to what happened with FDG [fluorodeoxyglucose]. When FDG first came out, it was only available in the big cities that we’re discussing. Now, the production is available virtually everywhere; you can get FDG virtually anywhere. I think that will be the case with PSMA agents sooner rather than later. To look just a little bit into the future, there is research on development of PSMA-targeted imaging agents using copper…which now have half-lives in the 3-4 hour range. With agents like that, you would need very few central sites to produce and deliver to the entire continental United States. I [foresee] current PSMA-targeted agents rapidly becoming available to places that currently don’t have [them], and the future generation of agents will make that even more so.

Transcript edited for clarity.