[C-11]choline PET/CT imaging in occult local relapse of prostate cancer after radical prostatectomy

Purpose The aim of this study was to assess the accuracy and clinical impact of [C-11]choline PET/CT for localizing occult relapse of prostate adenocarcinoma after radical prostatectomy. Methods Fourty-nine patients with prostate adenocarcinoma, radical prostatectomy, no evidence of metastatic disease, and occult relapse underwent [C-11]choline PET/CT. Thirty-six of the patients had biochemical evidence and histological evaluation of local recurrence. Thirteen patients had PSA < 0.3 ng/ml and no evidence of active disease after 1 year follow-up. Focal nodular [C-11]choline uptake in the prostatic fossa was visually assessed and graded on a five point scale. Maximum standardized radioactivity uptake value (SUVmax) and the lesion size were measured. A receiver operating characteristic (ROC) analysis was performed and the clinical impact of the PET/CT study was determined. Results [C-11]choline PET/CT was true positive in 23/33 patients and true negative in 12/13 controls. SUVmax of local recurrence was 3.0 (median, range 0.6-7.4) and 1.1 (0.4-1.6) in controls (p=0.0002). Lesion size was 1.7 cm (range 0.9-3.7). Area under the ROC curve for detecting relapse was 0.90 +/- 0.05 and 0.83 +/- 0.06 for visual evaluation and SUVmax, respectively. Sensitivity and specificity of [C-11]choline PET/CT were 0.73 and 0.88, respectively. [C-11]choline PET/CT identified 12/17 (71%) patients with a favourable biochemical response to local radiotherapy at 2 year (median, 0.8-3.2 range) follow-up. Conclusions Focally increased [C-11]choline uptake in the prostatic bed reliably predicted local low volume occult relapsing prostate adenocarcinoma after radical prostatectomy and identified 71% of patients with a favourable biochemical response to local radiotherapy.