[18F]choline positron emission tomography in prostate cancer patients with biochemical recurrence after radical prostatectomy: influence of antiandrogen therapy - a preliminary study.

OBJECTIVE: Our purpose was to evaluate whether antiandrogen therapy (AAT) influences [(18)F]choline PET results in patients with biochemical recurrence after radical prostatectomy (RPE). METHODS: Through a retrospective study we evaluated two groups of patients, both with histologically proven carcinoma of the prostate, who had undergone RPE and a subsequent [(18)F]choline PET because of biochemical failure (<4 ng/dl). One group consisted of 13 patients under AAT at the time of the PET examination (age range, 55-80 years; median, 68). The other group who had not undergone AAT consisted of 22 patients (age range, 48-72 years; median, 67). Our results were correlated with follow-up information related to histopathology, changes in prostate-specific antigen levels, other imaging modalities and clinical examination. Mean follow-up was 27 months. RESULTS: In patients who had undergone AAT, [(18)F]choline PET was true positive in eight out of 10 patients. The overall sensitivity in this group was 80%. In two cases [(18)F]choline PET turned out to be false negative, missing local relapse. Of the patients treated only with RPE, 10 out of 20 turned out to be true positive, resulting in a sensitivity of 50%.In all, in four patients biochemical recurrence could not be correlated to pathological findings in any of the available modalities. The difference in sensitivity between patients with and without AAT was statistically not significant (P=0.235). CONCLUSION: In patients with biochemical recurrence during AAT after RPE, [(18)F]choline PET can yield true-positive findings, even at prostate-specific antigen values of less than 4 ng/dl, and is an accurate technique for the detection of recurrence.