Abstract
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Introduction: Adenoid cystic carcinoma (ACC) is an uncommon and aggressive malignant epithelial tumor associated with a poor prognosis and few therapeutic options. This study was prospectively designed to evaluate the diagnostic performance of 68Ga-PSMA-617 PET/CT in comparison with 18F-FDG PET/CT and to assess the safety of and therapeutic response to PSMA radioligand therapy (RLT) in patients with ACC.
Methods: With ethical approval and written informed consent, 30 patients pathologically diagnosed with ACC were recruited to this study. Each patient underwent 68Ga-PSMA-617 PET/CT and 18F-FDG PET/CT within 1 week. The number and maximum standardized uptake value (SUVmax) of PET-positive lesions were recorded and compared. Patients who met the treatment criteria were eligible for RLT with 177Lu-labeled Evans blue-modified PSMA-617 (177Lu-EB-PSMA-617).
Results: 68Ga-PSMA-617 PET/CT showed a higher SUVmax of tumors in 1 primary ACC patient (9.8 vs. 6.3) and 10 patients with local recurrence (10.4 ± 3.8 vs. 6.3 ± 5.9, P = 0.135) than 18F-FDG PET/CT, but the difference was not statistically significant due to the small sample size. 68Ga-PSMA-617 PET/CT revealed a lower SUVmax of lesions (3.8 ± 2.3 vs. 6.6 ± 3.6, P < 0.001) and less PET-positive lesions (202 vs. 301, P < 0.001) than18F-FDG PET/CT in patients with lung metastasis. The value of 68Ga-PSMA-617 PET/CT in diagnosing brain, bone, lymph node and liver metastasis was slightly superior to 18F-FDG PET/CT, but the difference was not statistically significant. A 41-year-old patient diagnosed as meninx recurrence after surgery of the left lacrimal gland tumor achieved unexpectedly satisfactory response without prominent side effect after 2 cycles of 177Lu-EB-PSMA-617 RLT with a dosage of approximately 1.85 GBq (50 mCi) per cycle, and the SUVmax of tumor decreased significantly, from 7.0 prior treatment to 3.5 after the first treatment, and then to 1.3 after the second treatment.
Conclusions: 68Ga-PSMA-617 PET/CT is a valuable imaging modality for the diagnosis and staging of ACC and complements 18F-FDG PET/CT. PSMA RLT with 177Lu-EB-PSMA-617 maybe a promising treatment for ACC and is worthy of further investigation.