Anatomical mapping of lymph nodes in patients receiving salvage lymphadenectomy based on a positive 11C-choline positron emission tomography/computed tomography scan

Introduction: This paper aims to assess the diagnostic accuracy of an 11C-choline positron emission tomography/computed tomography (PET/CT) scan in the detection of lymph node (LN) metastases in patients with biochemical recurrence after radically treated prostate cancer (PCa), as compared to histology. The secondary goal is to depict spreading patterns of metastatic LNs in recurrent PCa.

Material and methods: A single center retrospective study comprising of 30 patients who underwent retroperitoneal and/or pelvic salvage lymph node dissection (LND) due to 11C-choline PET/CT-positive nodal recurrences after radical treatment (median Prostate Specific Antigen (PSA) 1.5 ng/ml, range 0.2-11.4). Positive nodes on the preoperative PET/CT scans were mapped and compared to post-operative pathology results.LNs were marked as true positive, false positive, true negative and false negative and a patient- and a region-based analysis was performed. Sensitivity, specificity and positive/negative predictive value (PPV/NPV) were calculated.

Results: Sixty positive LNs were detected on PET/CT with a median number of two positive nodes per patient (range 1-6). In 29 patients, a super-extended pelvic LND (PLND) was performed combined with a retroperitoneal LND (RPLND) in 13 of those cases. One patient underwent an inguinal LND. One hundred thirty-seven of 644 resected LNs contained metastases. The 11C-choline PET/CT scan correctly predicted 31 positive nodes (55%) while 25 nodes were falsely positive (45%). One hundred and six histologically proven metastatic nodes were not detected on the 11C-choline PET/CT scan (77%). Sensitivity, specificity, PPV and NPV of the 11C-choline PET/CT were 23%, 95%, 55% and 82%, respectively.

Conclusions: 11C-choline PET/CT has a relatively low detection rate and a moderate PPV for metastatic LNs in patients with biochemical recurrence after radically treated PCa.