RESUMO
BACKGROUND: PSMA expression is influenced by hormonal status. We evaluated changes in PSA and whole-body 68Ga-PSMA-11 PET/CT (WB-PSMA PET) after initiation of androgen receptor signaling inhibitors (ARSi). METHODS: Prospectively enrolled patients with metastatic castration-resistant prostate cancer (mCRPC) initiating ARSi underwent serial PSA measurements and WB-PSMA PET at baseline, 1-week, and 3-months post-ARSi. We correlated WB-PSMA PET metrics and PSA kinetics after ARSi to 1-year clinical outcome. RESULTS: Due to low enrollment rate, the study was closed before reaching the recruitment goal of 30 patients. Nine patients were enrolled. At 1-year, unfavorable outcome was documented in 6/9 (66%) patients. Nine/9 patients completed PSMA PET at 1-week, 5/9 at 3-months. Changes in PSA, PSMA-VOL, SUVmean and SUVmax were - 12%, + 5%, + 3%, and + 10% at 1-week, - 42%, - 16%, - 15% and - 17% at 3-months, respectively. CONCLUSIONS: Our prospective trial involving 9 mCRPC patients initiating ARSi did not show significant modulation of PSMA expression measured on WB-PSMA PET at 1-week. This study was registered on clinicaltrials.gov (NCT04279561).
RESUMO
The prostate-specific membrane antigen (PSMA) has been targeted for PET imaging and radioligand therapy (RLT) in patients with prostate cancer. Xerostomia is a common side effect of RLT because of the high salivary gland uptake of PSMA radioligands. Here, we aimed to determine the impact of monosodium glutamate (MSG) administration on PSMA-radioligand biodistribution within healthy organs and tumor lesions by using 68Ga-PSMA-11 PET imaging. Methods: Sixteen men with prostate cancer were randomized (1:1) into oral ingestion and oral topical application ("swishing") arms. Each subject underwent 2 68Ga-PSMA-11 PET/CT scans within 14 d under baseline and MSG conditions. The salivary glands and whole-body tumor lesions were segmented using qPSMA software. We quantified tracer uptake via SUVmean and SUVmax and compared parameters within each patient. Results: For the oral ingestion arm, salivary gland SUVmean and SUVmax decreased on average from the control scan to the MSG scan by 45% ± 15% (P = 0.004) and 53% ± 11% (P < 0.001), respectively. Tumor lesion SUVmean and SUVmax also decreased by 38% (interquartile range, -67% to -33%) and -52% (interquartile range, -70% to -49%), respectively (P = 0.018). Swishing had no significant effect on 68Ga-PSMA-11 accumulation in normal organs or tumor lesions. Conclusion: Oral ingestion but not topical application of MSG reduced 68Ga-PSMA-11 uptake in salivary glands. Tumor uptake also declined; therefore, the clinical application of MSG is unlikely to be useful in the framework of RLT.