Final analysis of a prospective trial on functional imaging for nodal staging in patients with prostate cancer at high risk for lymph node involvement

Abstract

Purpose: Accurate staging modalities to diagnose lymph node involvement in patients with prostate cancer (PCa) are lacking. We wanted to prospectively assess sensitivity, specificity, and positive predictive value (PPV) and negative predictive value of 11C-choline positron emission tomography (PET)-computed tomography (CT) and diffusion-weighted (DW) magnetic resonance imaging (MRI) for nodal staging in patients with PCa at high risk for lymph node involvement. Material and methods: In total, 75 patients with a risk Z10% but o35% for lymph node (LN) metastases (Partin tables) who had N0 lesions based on the findings of contrast-enhanced CT scans were included. Patients underwent 11C-choline PET-CT and DW MRI before surgery, which consisted of a superextended lymph node dissection followed by radical prostatectomy. LNs were serially sectioned and histopathologically examined after pankeratin staining. These results were used as the gold standard to compare with the imaging results. Results: Of 1,665 resected LNs (median ¼ 21, range: 7–49), 106 affected LNs (median ¼ 2, range: 1–10) were found in 37 of 75 patients (49%). On a region-based analysis, we found a low sensitivity of 8.2% and 9.5% and a PPV of 50.0% and 40.0% for 11C-choline PET-CT and DW MRI, respectively. The patient-based analysis showed a sensitivity of 18.9% and 36.1% for and a PPV of 63.6% and 86.7% 11C-choline PET-CT and DW MRI, respectively. Even when both imaging modalities were combined, sensitivity values remained too low to be clinically useful. Conclusions: Because of the low sensitivity, there is no indication for routine clinical use of either 11C-choline PET-CT or DW MRI for LN staging in patients with PCa, in whom CT scan findings were normal.