A pilot study of 68 Ga-PSMA-617 PET/CT imaging and 177Lu-EB-PSMA-617 radioligand therapy in patients with adenoid cystic carcinoma

Abstract

BackgroundThis pilot study was designed to evaluate the diagnostic value of 68 Ga-PSMA-617 and 18F-FDG PET/CT in adenoid cystic carcinoma (ACC) and to assess the safety and therapeutic response to PSMA radioligand therapy (RLT) in ACC patients.MethodsThirty patients pathologically diagnosed with ACC were recruited into the cohort. Each patient underwent 68 Ga-PSMA-617 and 18F-FDG PET/CT within 1 week. The number and SUVmax of PET-positive lesions were recorded and compared. Four patients accepted RLT using 177Lu-EB-PSMA-617, in a dosage of approximately 1.85 GBq (50 mCi) per cycle for up to 3 cycles.ResultsCompared with 18F-FDG, 68 Ga-PSMA-617 revealed more PET-positive extrapulmonary tumors (157 vs. 141, P = 0.016) and higher SUVmax (8.8 ± 3.6 vs. 6.4 ± 4.2, P = 0.027). However, 68 Ga-PSMA-617 revealed less PET-positive pulmonary lesions (202 vs. 301, P < 0.001) and lower SUVmax of tumors (3.1 ± 3.0 vs. 4.2 ± 3.9, P < 0.001) than 18F-FDG. The combination of 68 Ga-PSMA-617 and 18F-FDG can detect 469 PET-positive lesions, which was superior to each alone (469 vs. 359 vs. 442, P < 0.001). Two patients achieved remarkable response after PSMA RLT, while the other two patients showed reduced tumor uptake of recurrent foci, lung and liver metastases, whereas increased SUVmax of bone metastases.Conclusions68 Ga-PSMA-617 PET/CT is a valuable imaging modality for the detection of ACC and combining with 18F-FDG PET/CT will achieve a higher detection efficiency. PSMA RLT may be a promising treatment for ACC and is worth of further investigation.Trial registration: Diagnosis of Adenoid Cystic Carcinoma on 68 Ga-PSMA-617 PET-CT and Therapy With 177Lu-EB-PSMA-617 (NCT04801264, Registered 16 March 2021, retrospectively registered).URL of registry: https://clinicaltrials.gov/ct2/show/NCT04801264.