Detection of Synchronous Primary Malignancies with 68Ga-Labeled Prostate-Specific Membrane Antigen PET/CT in Patients with Prostate Cancer: Frequency in 764 Patients.

We evaluated the incidence of synchronous primary malignancies in patients undergoing 68Ga-labeled prostate-specific membrane antigen PET/CT for prostate cancer (PC). Methods: Reports for 764 PC patients were reviewed. Incidental lesions atypical for PC metastases and suggestive of a synchronous primary malignancy were identified. Follow-up was obtained to confirm etiology. Results: Lesions atypical for PC metastases were found in 49 (6.4%) of 764 patients, and a synchronous primary malignancy was confirmed in 5 patients (0.7%; 2 lung, 1 lymphoma, 1 thyroid, and 1 base of tongue). In 8 patients (1.0%), lesions were proven to be atypical metastases from PC. In 24 patients (3.1%), lesions had a benign etiology. Follow-up was not available in 12 patients (1.6%). Conclusion: Synchronous 68Ga-labeled prostate-specific membrane antigen-avid malignancies were rare (0.7%) in PC patients; atypical lesions were more commonly unusual PC metastases (1.0%) or benign (3.1%).