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

BACKGROUND: This pilot study was designed to evaluate the diagnostic value of (68) Ga-PSMA-617 and (18)F-FDG PET/CT in adenoid cystic carcinoma (ACC) and to assess the safety and therapeutic response to PSMA radioligand therapy (RLT) in ACC patients. METHODS: Thirty patients pathologically diagnosed with ACC were recruited into the cohort. Each patient underwent (68) Ga-PSMA-617 and (18)F-FDG PET/CT within 1 week. The number and SUVmax of PET-positive lesions were recorded and compared. Four patients accepted RLT using (177)Lu-EB-PSMA-617, in a dosage of approximately 1.85 GBq (50 mCi) per cycle for up to 3 cycles. RESULTS: Compared with (18)F-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 (18)F-FDG. The combination of (68) Ga-PSMA-617 and (18)F-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. CONCLUSIONS: (68) Ga-PSMA-617 PET/CT is a valuable imaging modality for the detection of ACC and combining with (18)F-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 (177)Lu-EB-PSMA-617 (NCT04801264, Registered 16 March 2021, retrospectively registered). URL of registry: https://clinicaltrials.gov/ct2/show/NCT04801264.