Diagnostic performance of conventional MRI using T1W and T2W for primary lymph node staging in intermediate- and high-risk prostate cancer patients prior to pelvic lymph node dissection.

[PURPOSE] To assess the accuracy of conventional MRI with T1- and T2-weighted sequences in detecting lymphatic nodal spread (N1) in intermediate- and high-risk prostate cancer (PCa) patients via morphological criteria alone, extended pelvic lymph node dissection (ePLND) was used as the reference standard.

[METHODS] This prospective observational study included patients between 2009 and 2016 with intermediate- and high-risk PCa according to the D'Amico criteria and an estimated risk of N1 > 20% on the basis of the Briganti nomogram. All patients underwent MRI prior to ePLND. Interobserver analysis was conducted across three centers.

[RESULTS] Ninety-nine men, mean age 67 (5.7 SD), 93% high-risk PCa patients and 39.4% with N1 disease, according to ePLND, were evaluated. The pooled sensitivity of MRI for detecting N1 was 24.6% (95% CI: 16.3-35.1), whereas the pooled specificity was 95% (95% CI: 85.3-98.8). Interobserver agreement was moderate (Fleiss' κ = 0.56). All readers failed to identify patients with high-volume N1, and the identification of those with a high number of N1 events was inconsistent across readers. The strengths of this study include the high number of N1 cases, with a median of 17 (6-40) harvested lymph nodes per participant. Limitations include the time interval between MRI and ePLND (median of 44 days) and the lack of standardized lymph node evaluation criteria, reflecting real-world clinical practice.

[CONCLUSION] MRI using only T1W and T2W sequences has demonstrated limited effectiveness in lymph node staging for intermediate- and high-risk prostate cancer, even in high-volume metastatic disease. Additionally, interobserver analysis shows only moderate agreement.