11C-choline PET/CT scan in patients with prostate cancer treated with intermittent ADT: A sequential PET/CT study

AIM: The purpose of this preliminary study was to evaluate the usefulness of 11C-choline PET/CT in patients with recurrent prostate cancer and hormone-sensitive disease treated with intermittent antiandrogen therapy scheme. PATIENTS AND METHODS: We retrospectively evaluated 10 patients after radical prostatectomy (n = 8) or external beam radiotherapy (n = 2) as primary therapy, studied with sequential 11C-choline PET/CT. The first PET/CT (PET1) was performed during antiandrogen therapy (ADT) and the second PET/CT (PET2) was performed after therapy interruption. Only patients with negative results at PET1 were included in the study. At the time of PET1, all patients were under ADT from at least 6 months (mean PSA 0.54 ng/mL). At the time of PET2, all patients had completed ADT for a mean period of 7 months. 11C-Choline PET/CT findings were validated by a follow-up of at least 12 months or histological confirmation in case of local relapse. RESULTS: PET2 has been able to detect the site of recurrences in all cases. At the time of PET2, mean PSA was 3.88 ng/mL; mean PSAdt was 2.46 months; and mean PSAvel was 6.94 ng/mL/year. Four out of 10 patients showed a single lesion, 5 out of 10 patients showed 2 lesions and 1 patient showed multiple lymph-node lesions. CONCLUSION: When performed during ADT interruption, 11C-choline PET/CT has been able to detect the site of recurrence in patients with increasing PSA values. In this context, 11C-choline PET/CT may help to assess the burden of disease or to change the therapeutic approach using more aggressive and addressed therapies like guided RT or salvage lymph-node dissection.