Effect of understaging on local recurrence of rectal cancer

Background and Objectives Magnetic resonance imaging of the pelvis has a limited accuracy to detect positive lymph nodes but does dictate neoadjuvant treatment in rectal cancer. This study aimed to investigate preoperative lymph node understaging and its effects on postoperative local recurrence rate. Methods Patients were selected from a retrospective cross‐sectional snapshot study. Patients with emergency surgery, cM1 disease, or unknown cN‐ or (y)pN category were excluded. Clinical and pathologic N‐categories were compared and the impact on local recurrence was determined by multivariable analysis. Results Out of 1548 included patients, 233 had preoperatively underestimated lymph node staging based on (y)pN category. Out of the 695 patients staged cN0, 168 (24%) had positive lymph nodes at pathology, and out of the 594 patients staged cN1, 65 (11%) were (y)pN2. Overall 3‐year local recurrence rate was 5%. Clinical N‐category was not associated with local recurrence when corrected for pT‐category, neoadjuvant therapy, and resection margin, neither in patients with (y)pN1 (hazard ratio [HR]: 1.67 (95% confidence interval [CI]: 0.68‐4.12) P = .263) nor (y)pN2‐category (HR: 1.91 95% CI: [0.75‐4.84], P = .175). Conclusion Preoperative understaging of nodal status in rectal cancer is not uncommon. No significant effect on local recurrence or overall survival rates were found in the present study.