Sensitivity of fluorine-18-fluoromethylcholine PET/CT to prostate-specific antigen over different plasma levels: a retrospective study in a cohort of 192 patients with prostate cancer

Purpose Several factors have been identified that predict positive fluorine-18-fluoromethylcholine (18F-FCH) PET/CT result in patients with prostate cancer undergoing PET/CT for biochemical failure. Among these factors, prostate-specific antigen (PSA) is the single factor most consistently associated with the prediction of positive 18F-FCH PET/CT. In this study, we wished to confirm this finding and expand it in a large series of patients. Patients and methods We retrospectively analyzed 192 patients with prostate cancer who were recruited from the Nuclear Medicine Department of the Sant’Andrea Hospital of La Spezia, Italy, from March 2013 to March 2018 and who underwent 18F-FCH PET/CT owing to biochemical failure after radical prostatectomy. Results Median trigger PSA was 2.57 ng/ml. The overall positive detection rate of 18F-FCH PET/CT was 60.9%. The percent of positive scans was 30.5% for PSA less than 1 ng/ml, 59.4% (38/64) for PSA between 1 and 5 ng/ml, and 88.4% for PSA greater than 5 ng/ml (P<0.001). On univariate regression analysis, high PSA levels, biochemical failure during antiandrogenic therapy at the time of PET/CT, and older age significantly (P<0.05) predicted positive 18F-FCH PET/CT result. On multivariate regression analysis, only high PSA levels and biochemical failure during antiandrogenic therapy maintained the statistical significance (P<0.05). However, when the analysis was restricted to patients with PSA less than 1 ng/ml, PSA lost the statistical significance. Receiver operating characteristic analysis revealed an area under the curve of 0.795. The PSA cutoff value that best distinguished PET/CT-positive from PET/CT-negative patients was 2.57 ng/ml. Sensitivity and specificity at this PSA value were 66.7 and 76.0%, respectively. Conclusion This study confirms that PSA robustly predicts positive PET/CT result with radiolabeled choline. Unfortunately, this study also confirms the limited sensitivity of 18F-FCH PET/CT for PSA less than 1 ng/ml, which currently represents the weakest point of the technique.