18F-Fluoroethylcholine PET/CT identifies lymph node metastasis in patients with prostate-specific antigen failure after radical prostatectomy but underestimates its extent.

Abstract

The detection of lymph node metastases (LNMs) is one of the biggest challenges in imaging in urology. To evaluate the accuracy of combined 18F-fluoroethylcholine (FEC) positron emission tomography (PET)/computed tomography (CT) in the detection of LNMs in prostate cancer (PCa) patients with rising prostate-specific antigen (PSA) level after radical prostatectomy. From June 2005 until November 2011, 56 PCa patients with biochemical recurrence after radical prostatectomy underwent bilateral pelvic and/or retroperitoneal lymphadenectomy based on a positive 18F-FEC PET/CT scan. The findings of PET/CT were compared with the histologic results. Median PSA value at the time of 18F-FEC PET/CT analysis was 6.0 ng/ml (interquartile range: 1.7-9.4 ng/ml). In 48 of 56 (85.7%) patients with positive 18F-FEC PET/CT findings, histologic examination confirmed the presence of PCa LNMs. Of 1149 lymph nodes that were removed and histologically evaluated, 282 (24.5%) harbored metastasis. The mean number of lymph nodes removed per surgical procedure was 21 (standard deviation: ± 18.3). A lesion-based analysis yielded 18F-FEC PET/CT sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 39.7%, 95.8%, 75.7%, and 83.0%, respectively. A site-based analysis yielded sensitivity, specificity, PPV, and NPV of 68.4%, 73.3%, 81.3%, and 57.9%, respectively. Patients with negative PET/CT did not undergo surgery, thus sensitivity, specificity, and negative predictive value on a patient basis could not be calculated. A positive 18F-FEC PET/CT result correctly predicted the presence of LNM in the majority of PCa patients with biochemical failure after radical prostatectomy but did not allow for localization of all metastatic lymph nodes and therefore was not adequately accurate for the precise estimation of extent of nodal recurrence in these patients.