A Case Report of Incidental Thyroid Cancer Metastasis Detected in a PSMA PET/CT Scan of a Prostate Cancer Patient: Predicting RAI-Refractoriness.

Early recognition of patients at risk for radioactive iodine refractoriness (RAIR) is essential, as these individuals often face a poorer prognosis. Consequently, there is a pressing need for advanced therapeutic options in aggressive thyroid cancer cases. We present a case involving a 57-year-old male with prostate adenocarcinoma who, through prostate-specific membrane antigen (PSMA) PET/CT scanning, was incidentally found to have a PSMA-avid lung nodule. Subsequent biopsy confirmed metastatic thyroid carcinoma. Following two sessions of radioactive iodine (RAI) therapy, posttherapy scans showed a noniodine-avid lung nodule. The PSMA-avid lung lesion indicates an aggressive disease form likely to develop RAI resistance, which was subsequently confirmed. This finding suggests that PSMA expression could be an effective early predictor of RAIR. Moreover, the PSMA avidity of these lesions supports the use of Lutetium-177-PSMA therapy, expanding treatment options for RAIR-differentiated thyroid carcinoma (DTC).