Using Gallium PSMA PET to Evaluate Progression and Eligibility for Lutetium-177 PSMA Therapy - Bennett Chin

January 24, 2023

In this Society of Nuclear Medicine and Molecular Imaging (SNMMI) case of the month lecture, Bennett Chin presents a patient case of a 73-year-old man with advanced prostate cancer at diagnosis who was referred for a gallium PSMA PET CT to evaluate for progression as well as to evaluate eligibility for lutetium-177 PSMA. Despite persistent disease, this patient has a low PSA on presentation. Dr. Chin reviews this patient's profile and details his eligibility for PSMA therapy based on PSMA uptakes rather than PSA.

Biographies:

Bennett Chin, MD, Professor, Radiology_Nuclear Medicine, the University of Colorado Anschutz Medical Center, Denver, CO


Read the Full Video Transcript

Bennett Chin: Welcome. My name is Bennett Chin. I'm a faculty member in the Department of Radiology in Nuclear Medicine at the University of Colorado in Denver. And it's my pleasure to present to you the first Case of the Month in SNMMI. It's entitled, Using Gallium PSMA PET to Evaluate Progression and Eligibility for Lutetium-177 PSMA therapy.

This patient is a 73-year-old man with advanced prostate cancer at diagnosis. He actually presented with pneumonia in 2019 and was otherwise asymptomatic. Incidentally noted was an elevated PSA and subsequent workup with a biopsy revealed adenocarcinoma Gleason Grade 4+5 in 11 of 12 cores. A subsequent MRI showed extracapsular extension, seminal vesicle involvement, right iliac lymph node involvement, and he was staged clinically T3a, N1, M1. He started therapy and had radiation therapy, ADT and enzalutamide and failed several of those, including docetaxel, and went on to clinical trial. His PSA in October of 2022, right around the time of his scan was 0.8 nanograms per ml. He presented with a slight increase in size of a right iliac node on CT and this was suspected as progression.

So he was referred for a gallium PSMA PET CT to evaluate for progression as well as to evaluate eligibility for lutetium-177 PSMA. Here on this slide we can see that there is normal uptake in the prostate bed, low back down activity, mildly heterogeneous. However, a little bit more superiorly in the right common iliac lymph node region. You can see intense focal uptake in two iliac nodes with SUV max 23.4.

A little bit more superiorly, you can see intense focal uptake at the periphery of the sclerotic lesions. There's intense focal uptake in a non-sclerotic area, SUV max of 23.4. Very intense uptake. And again, more superiorly, another focus of intense uptake at the periphery of a sclerotic lesion, SUV max of 21.6. And more superiorly in the lower cervical region, you can see that there's intense bilateral supraclavicular lymph nodes. They're positives. There's intense focal uptake with a SUV max of 9.0.

So as a summary, this patient's PSMA had a very variable course. He initially presented with stage four disease, clinical stage T3a, N1, and M1. And at initial diagnosis at an outside hospital in 2019, his PSA was over 180. After ADT/enzalutamide, radiation therapy a couple months later, this went down and nadired at 0.6. When he presented to us in 2020, his PSA was 32.0. He went on therapy and the PSA decreased to 0.8. And this shows that despite persistent disease, this patient has a low PSA on presentation.

So we know from early studies that patients with early biochemical recurrence can have a lower detectability rate if their PSA presentation is low. However, high risk patients can remain with a reasonably high detectability rate, even if their PSA level is low. In patients with advanced disease who are potential candidates for Lutetium PSMA, PSMA PET scans are appropriate. A low PSA should not exclude these candidates, especially if they are advanced prostate cancer patients. Eligibility for a future PSMA is based on PSMA uptake and not on the certain PSA. These patients may have extensive disease as shown in this case and are good candidates for PSMA therapy.

On behalf of the SNMMI Prostate Cancer Outreach Working Group, we hope you found this presentation educational and we thank you for your attention.

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