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

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.

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.

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.

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.