Relevance of magnetic resonance imaging-detected pelvic sidewall lymph node involvement in rectal cancer

Background: The significance of magnetic resonance imaging (MRI)-suspected pelvic sidewall (PSW) lymph node involvement in rectal cancer is uncertain. Methods: Magnetic resonance images were reviewed retrospectively by specialist gastrointestinal radiologists for the presence of suspicious PSW nodes. Scans and outcome data were from patients with biopsy-proven rectal cancer and a minimum of 5 years' follow-up in the Magnetic Resonance Imaging and Rectal Cancer European Equivalence Study. Overall disease-free survival (DFS) was analysed using the Kaplan-Meier product-limit method and stratified according to preoperative therapy. Binary logistic regression was used to match patients for propensity of clinical and staging characteristics, and further survival analysis was carried out to determine associations between suspicious PSW nodes on MRI and survival outcomes. Results: Of 325 patients, 38 (11.7 per cent) had MRI-identified suspicious PSW nodes on baseline scans. Such nodes were associated with poor outcomes. Five-year DFS was 42 and 70.7 per cent respectively for patients with, and without suspicious PSW nodes (P < 0.001). Among patients undergoing primary surgery, MRI-suspected PSW node involvement was associated with worse 5-year DFS (31 versus 76.3 per cent; P = 0.001), but the presence of suspicious nodes had no impact on survival among patients who received preoperative therapy. After propensity matching for clinical and tumour characteristics, the presence of suspicious PSW nodes on MRI was not an independent prognostic variable. Conclusion: Patients with suspicious PSW nodes on MRI had significantly worse DFS that appeared improved with the use of preoperative therapy. These nodes were associated with adverse features of the primary tumour and were not an independent prognostic factor.