Lower lymph node yield following neoadjuvant therapy for rectal cancer has no clinical significance

Background: Obtaining 12 lymph nodes following resection for rectal cancer is an important prognostic marker. However, patients who have received neoadjuvant therapy are known to have a lower lymph node yield. We conducted this study to determine the clinical significance of evaluating <12 versus >= 12 lymph nodes in individuals who underwent surgery following neoadjuvant therapy for rectal cancer. Methods: A retrospective analysis of all patients who received neoadjuvant therapy for locally advanced rectal cancer between January 2008 and December 2014 followed by proctectomy was conducted. Results: In total, 217 patients were treated for rectal cancer. Mean follow-up was 23.4 (interquartile range, 9-40.5) months. Sixty-three (29.0%) patients received neoadjuvant therapy. There was a statistically significant difference in the number of patients with <12 lymph node yield between those who received neoadjuvant therapy and those who did not (27.0% vs. 9.1%, P=0.001). Amongst the 63 patients who received neoadjuvant therapy, lymph node yield of >= 12 was not associated with a statistically significant difference in time to recurrence [hazard ratio (HR) 0.17; 95% confidence interval (CI), 0.01-2.01, P=0.160] or time to death (HR 1.07; 0.15-7.90, P=0.946). Kaplan-Meier curves also did not show any significant difference between those with <12 lymph nodes and those with >= 12 lymph nodes in terms of recurrence and death (P=0.203 and P=0.762 respectively). Conclusions: Although neoadjuvant therapy reduces the lymph node yield during surgery for locally advanced rectal cancer, this has no significance on the overall survival of the patient.