Sensitivity and specificity of PET/CT regarding the detection of lymph node metastases in prostate cancer recurrence

BACKGROUND: The aim of the study is to assess the efficacy of choline PET/CT regarding the detection of lymph node (LN) metastases in recurrent prostate cancer (PCa). METHODS: 49 patients with a biochemical recurrence of PCa (PSA >0.2 ng/ml) were included in the study. All patients were selected for further diagnostics with a choline-PET/CT. All patients underwent salvage extended lymphadenectomy. The PET/CT result and the histological findings were analyzed regarding the specificity and sensitivity and with respect to the localization of the metastases. The detection rate of LN metastases was analyzed with respect to interdependencies between the pre-PET/CT PSA-value as well as the role of prior ADT. RESULTS: 41 out of 49 (83.6%) patients showed positive PET/CT results. Positive LNs were found in 27 out of 49 patients (55.1%). 48.9% of the PET-CT-findings proved true positive, 36.7% were found to be false positive. 8.1% proved true negative and 8.1% false negative. This results in a specificity of 22.7% and a sensitivity of 85.1%. Out of the true positive PET/CT scans, 61.9% were not congruent regarding the localization of positive LNs. In patients with PSA [greater than or equal to] 5 ng/ml, the sensitivity of the PET/CT result was 93.7%, while specificity was 0%. In 24 patients who underwent ADT prior to the PET/CT diagnostics, the sensitivity was 84.6% and specificity 9.0%. CONCLUSIONS: The reliability of PET/CT imaging for detection of LN metastases is limited by a high false-positive rate. The influence of ADT further diminishes the PET/CT reliability. Sensitivity of the PET/CT is highest in patients with a PSA of [greater than or equal to] 5 ng/ml. Based on our results, we propose the following conclusions: 1. There is no well-established diagnostic alternative to Choline-PET/CT Scan. Therefore this method may continue to be performed in patients with BCR. 2. It is not sufficient to remove only those LNs that show up in the PET/CT. 3. Salvage extended lymphadenectomy should follow a predefined template (e.g. the “Kiel template”) and not just the PET/CT scan results.