According to reports, re-staging of patients suffering from prostate cancer by positron emission tomography (PET) using C-11-choline has failed to produce positive findings at a PSA level of < 5 ng/ml. Hence, the purpose of our study has been to determine whether this is true also for PET/CT using F-18-fluorocholine (FCH PET/CT) or whether it is possible to obtain true positive results by FCH PET/CT even at lower PSA levels.
Methods: In 34 patients with prostate cancer who had undergone initial therapy (radical prostatectomy n = 31, radiotherapy n = 3), a PET/CT scan was performed using F-18-fluorocholine (FCH) during follow-up in case of demonstrable or rising PSA levels. Current PSA levels were determined in all patients at the time of examination.
Results: Median PSA in FCH positive patients was 6.1 ng/ml (mean PSA 17.1 ng/ml), median PSA in FCH negative patients was 2.3 ng/ml (mean PSA 3.4 ng/ml), respectively (p < 0.05). In eight of 17 examinations (47%) with PSA < 5 ng/ml, at least one FCH-positive focus was detected. So far the findings could be confirmed by correlating imaging methods (CT and/or MR), biopsy/histology and the course of the disease, respectively, in seven of the eight FCH-positive cases with PSA < 5 ng/ml, so that a true positive FCH PET/CT finding was obtained all in all in seven of 17 (41%) examinations with PSA < 5 ng/ml. In four of these seven FCH PET-positive patients with PSA < 5 ng/ml, adjuvant hormonal therapy was administered at the time of the examination or prior to the examination.
Conclusion: In re-staging patients with prostate cancer, FCH PET/CT is able to yield true positive findings even at PSA < 5 ng/ml. Therefore, FCH PET/CT should not be restricted to patients with PSA > 5 ng/ml.