Detection of a second primary cancer in a 18F-fluorocholine PET/CT - multicentre retrospective analysis on a group of 1345 prostate cancer patients.

Background: Aim of this study was to evaluate the rate of incidental detection of second primary cancer (SPC) at 18F-fluorocholine ([18F]FCH) positron emission tomography/computed tomography (PET/CT) performed in prostate cancer patients.

Material and methods: A retrospective analysis was performed on a group of 1345 prostate cancer patients, who underwent [18F]FCH PET/CT study because of suspicion of recurrence (n = 937) or for initial staging (n = 408). Images were acquired after intravenous injection [18F]FCH with a mean activity of 200 ± 75 MBq (5.4 ± 2 mCi), from the top of the head to the half of the thigh. The confirmation of second primary cancer was obtained from the cancer registry.

Results: Based on the [18F]FCH PET/CT scans, a second primary cancer was suspected in 89 patients (6.6%). Of these, a malignancy was histologically confirmed in 26 patients (29% of all suspected findings and 1.9% of the complete cohort). Lung cancer (including adenocarcinoma, neuroendocrine cancer) was diagnosed in 13 patients (50%) and hematologic neoplasm (including chronic lymphocytic leukemia, Hodgkin lymphoma, follicular lymphoma, and multiple myeloma) in 5 patients (19%). 18F-fluorocholine PET/CT also revealed esophageal cancer, mesothelioma, testicular, renal, bladder, and colorectal cancer inindividual patients, non-keratinizing squamous cell carcinoma (SCC) of the skin as well as head and neck SCC with unknown primary.

Conclusion: We conclude that incidental detection of a second primary cancer in prostate cancer patients using [18F]FCH PET/CT is not very common and that lung cancer and hematologic malignancies are most frequently detected.