Is 11C-choline PET/CT Accurate to Detect Nodal Relapses of Prostate Cancer After Biochemical Recurrence?

One option for restaging prostate cancer (PCa) patients with biochemical recurrence (BCR) after radical treatment is represented by 11C-choline positron emission tomography/computed tomography (PET/CT). An early detection of nodal relapses from PCa as the only metastatic site could candidate patients for salvage lymph node dissection (sLND), which has been proposed as a treatment option to delay tumor progression and thus postpone hormonal therapy.

However, divergent results have been published in the literature about the reliability of PET/CT in restaging BCR patients, especially regarding the localization of positive lymph nodes between PET/CT and surgery. In our retrospective study we aimed to assess the accuracy of PET/CT in predicting the site of nodal relapses in patients undergoing pelvic and/or retroperitoneal sLND, in a multicentric series of 106 patients. All patients but six had a PET/CT showing at least one nodal recurrence and received sLND. Overall, PET/CT detected a mean of two positive nodes per patient, whereas the mean number of nodes removed during surgery was 21.7, with an average of 4.7 positive nodes.

A lesion-based analysis of sensitivity, specificity, and accuracy of PET/CT revealed values of 61.6%, 71.9%, and 70.2%, respectively. PET/CT sensitivity was 75.5% in the lower pelvis, while the retroperitoneum showed a high specificity (95%). More in detail, sLND did not find any positive nodes in 16 patients (15%), while it found positive nodes in five out of six patients with a negative PET/CT. Regression analyses showed an overall discriminative accuracy of 70.4% for PET/CT. On the other hand, a patient-based analysis revealed a high sensitivity of 94.4%. In other words, according to our results PET/CT might be correct in identifying a patient with a nodal recurrence, but unreliable about the nodal region involved, implying a significant limitation in the ability to define the extension of sLND only on the basis of the location of PET/CT-positive nodes.

Irrespectively of PET/CT results, we were not able to find anatomic regions in the pelvis predictive of retroperitoneal involvement during sLND, therefore no threshold could be identified to proceed with retroperitoneal sLND. Therefore, it is advisable to adopt an extended template including pelvic and retroperitoneal regions when performing sLND, keeping in mind the potential comorbidities of an extended surgery.

Written by: Marco Oderda¹, Paolo Gontero¹
1. Urology Clinic, Città della Salute e della Scienza di Torino, Department of Surgical Sciences, University of Turin, Italy.

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