Akintunde Orunmuyi: I am Akintunde Orunmuyi, I'm a nuclear medicine physician at the Kenyatta University Teaching Research Referral Hospital in Nairobi, Kenya. I'm happy to present the second in the series of the SNMMI case of the month, and I'll be explaining the heterogeneity of PSMA uptake in prostate cancer.

I'm presenting a 75-year-old gentleman who was first seen in the clinic with an indexed PSA of 35 nanograms per milligrams. Multiparametric MRI showed extra capsular involvement and a solitary left external iliac lymph node. He was staged as T4N1Mx. Abdominal MRI also showed a well-defined cystic mass in the liver with no abdominal lymph nodes. Biopsy confirmed prostate adenocarcinoma, Gleason grade 5 + 4 disease.

A PSMA PET scan was ordered for distant staging. The PSMA PET scan showed heterogeneous uptake in the prostate in keeping with known primary prostate cancer. From this image, you can also get a hint of bone metastasis. PSMA also demonstrated regional lymph nodes with heterogeneous PSMA uptake and distant regional lymph nodes. This image shows the spine profile of sclerotic changes in the spine with increased PSMA uptake in keeping with metastasis, and it also shows heterogeneous uptake in the bone lesions. The liver lesion was non-PSMA avid and is consistent with a benign cystic mass in the liver.

To summarize, I have presented a patient with advanced prostate cancer who has not received any treatment. Notably, his serum PSA was low in comparison to the extent of disease on PSMA PET/CT scan. The PSMA scan upstaged this patient to T4M1aM1b and it showed heterogeneous PSMA uptake, which was defined by both low and high PSMA lesions in the same scan. We used the PROMISE criteria to establish the uptake and the level of uptake of these lesions, and it's shown in the box below.

Increasingly, heterogeneous PSMA expression is prevalent in the settings of metastatic prostate cancer. The main hypothesis has been linked to defective DNA repair, such that cells that have defective DNA repair express more PSMA, and so, may respond to treatments that generate double-stranded breaks. This case highlights the promise of PSMA PET/CT for a better understanding of prostate cancer. I'd like to thank the SNMMI Prostate Cancer Outreach Working Group and acknowledge their contributions to this presentation. Thank you.