Advances in PSMA-Targeted PET Imaging for Prostate Cancer - Episode 6

Sequencing of Conventional and PSMA-PET Imaging in Prostate Cancer

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Citing recent guidelines recommendations, urologists share how they approach sequencing of conventional and PSMA-PET imaging for patients with prostate cancer, and discuss how use of each modality might affect subsequent patient management and treatment decisions.


Gerald Andriole, MD: There are a fair number of treatment alteration trials using PET [positron emission tomography] scans after conventional imaging in patients with biochemical recurrence. Knowledge of the PET scan findings result in a major treatment change in two-thirds of men. There are major changes in going from palliative systemic therapy to targeted potentially curable therapy compared with the reverse. A positive PET scan is more informative than a negative PET scan or a PET scan that doesn’t show anything. Depending upon the clinical context, it has substantially changed the management of the biochemically recurrent patient.

I’ll put an asterisk with that. We don’t know if this is going to translate into improved overall survival. It sounds like it should, but that hasn’t been proven. For many men, it reduces the morbidity or adverse effects. With salvage radiation therapy, for example, it’s targeted in the case of a patient who had a PET scan vs whole pelvic or otherwise in a man who had negative conventional imaging but a lot of adverse findings on his radical prostatectomy.

Gary Ulaner, MD, PhD, FACNM: To throw in the demonstrative case, when looking at biochemical recurrence in which a patient postprostatectomy would get pelvic salvage radiation in the next line, the PSMA [prostate-specific membrane antigen]–PET demonstrates a solitary sternal metastases. You would entirely change where the patient is going to get treated, and they get the effective radiation to the site of disease and prevent the potential adverse effects in the pelvis. Those are examples when, in biochemical recurrence, a single PSMA-PET scan entirely changes the patient’s treatment plan and results in efficacy and adverse effects.

David Albala, MD: It’s a game changer in that scenario too. It prevents the morbidity of treatment in 1 area for appropriate treatment in the area where the metastasis is. Ashley, I’m going to ask you this, but I think I know the answer. How do you sequence PSMA testing? Do you do conventional imaging? You’re in the Midwest. How do the sequencing and appropriateness of doing this imaging play out in Chicago?

Ashley Ross, MD, PhD: I’m lucky that most of the pair groups—not all, but most—have looked closely at the Society of Nuclear Medicine & Molecular Imaging Practice Guidelines and the NCCN [National Comprehensive Cancer Network] Guidelines. They’re saying that PET-PSMA imaging in these different buckets—initial staging, chemical recurrence—is the most accurate staging. Because of that, you save cost. With the pro-PSMA study, you save radiation dose of a patient. They’re allowing me with very minimal resistance to get PET-PSMA imaging as my initial staging.

When I was starting out a year ago, when the approvals were more fresh, I was getting conventional or older imaging with the CT axial imaging and MDP [methylene diphosphonate] bone scan. If it was questionable or negative, but I had high suspicion, I would then get the PET. Now, it’s reverse. I’m getting the PET-PSMA first. If I have a question or 2, if it doesn’t make sense to me, I’ll sometimes reach for MDP bone scans. If it’s important enough, like the theoretical—or maybe not theoretical—case that Gary just talked about, and I’m not sure what’s going on with the solitary sternum, I’m having my interventional radiologist biopsy to figure it out.

Regardless, the better imaging is first. If someone came into my office and I thought they had lung cancer, because they’re coughing up blood, and I want to do my best first imaging, I probably wouldn’t reach for an x-ray as often as a CT. I’m reaching for the better PET imaging first. That’s what the guidelines suggest. In fact, the latest version of the NCCN Guidelines—the ones that are about to come out in 2023—have the clarification that you don’t the older imaging prior to doing this PET-PSMA. We don’t want our patients getting MRI or CT bone scan and then a PET. The best would be an MRI prior diagnosis and then a PET scan if their case warrants imaging.

Gerald Andriole, MD: I agree completely. The NCCN, for example, has stated unambiguously in the treatment guidelines that the enhanced sensitivity of PSMA-PET scans should not be a requirement to have negative or ambiguous conventional imaging to go forward with a PSMA-PET scan. Having said that, last week I had to do a peer to peer discussion with a urologist. He was very apologetic. He says, “I understand what you’re saying. But the Medicare policy that this particular patient had, notwithstanding the NCCN and everything we’ve been talking about, requires negative or ambiguous conventional imaging.” We’re in the process of putting this guy through the second-best form of imaging for prostate cancer staging.

David Albala, MD: Gary, how about the urologist in California? Are they able to go directly to this type of imaging? Or as Gerry has encountered on the East Coast, do you have to do conventional imaging first?

Gary Ulaner, MD, PhD, FACNM: I won’t speak for all of the West Coast, but in our area, we go directly to PSMA and PET. There’s no need to get the CT and bone scan prior to a PSMA-PET. Our urologists have greatly appreciated the ability to do so.

David Albala, MD: The urology community is embracing this technology. Word is out that this imaging is quite good.

Transcript edited for clarity.