Purpose: To examine the association between the number of lymph nodes retrieved and oncologic outcome after preoperative chemoradiation for rectal cancer according to tumor regression grade.
Methods: Patients with rectal cancer who underwent curative surgery between May 2004 and December 2012 were analyzed retrospectively. Using multivariate analysis, the correlation between clinicopathologic variables and the number of lymph nodes retrieved was evaluated. The associations between the oncologic outcome and number of lymph nodes retrieved were also investigated according to the tumor regression grade.
Results: In total, 1,332 patients were identified, of whom 433 (32.8 %) received preoperative chemoradiation. Multivariate analysis revealed that preoperative chemoradiation was an independent predictor of the number of lymph nodes retrieved (P = 0.002). After chemoradiation, the number of total and positive lymph nodes retrieved was inversely correlated with tumor regression. Retrieval of ≥12 lymph nodes was not an independent prognostic factor for disease-free survival; however, among patients with a good tumor response, those with <12 lymph nodes retrieved had a significantly better 3-year disease-free survival (P = 0.030) than those with ≥12 lymph nodes retrieved.
Conclusions: Reduced lymph node yield after preoperative chemoradiation for rectal cancer does not indicate inadequate oncologic surgery. It may represent good treatment response and better prognosis, especially in patients with good pathologic tumor regression after chemoradiation.