Original researchImpact of lymph node ratio and number on survival in patients with rectal adenocarcinoma after preoperative chemo radiation

•Preop chemoradiation reduces node retrieval in rectal cancer with no impact on survival.•Is this true for younger patients with predominance of low rectal tumors?•What specific lymph node ratio predicts survival in this group?•Our results show that number of extracted nodes does not affect survival.•Lymph node ratio impacts survival but a specific ratio needs to be defined.

Background: Retrieval of <12 lymph nodes after proctectomy and preoperative chemoradiation (C-XRT) may improve survival in good risk patients. The objective of this study was to determine impact of <12 retrieved lymph nodes and lymph node ratio (LNR) on survival in a population with certain poor prognostic features for rectal cancer. Methods: Patients who underwent surgery for rectal adenocarcinoma between 2005 and 2011 were divided them into <12 or >12 lymph node groups. The LNR groups were based on interquartile range. Clinicopathological and treatment outcomes were compared. Expected 5 year disease free and overall survival was calculated. Cox proportional hazard model was used to determine independent predictors. Results: More patients in <12 lymph nodes removed group had low tumors (<5 cm from anal verge) (75.5% versus 60.7%) (P = 0.03) and underwent abdominoperineal resection (59.1% versus 42.9%) (P = 0.02). Overall survival (OS) and disease free survival (DFS) was not different [(56% and 52% (P = 0.7)] [(50% and 57% (P = 0.5)]. LNR <0.15 was independent predictor of DFS while LNR ratio <0.12 for OS on multivariate analysis. Conclusion: LNR and not number of retrieved nodes impacts survival in younger patients with predominance of anorectal tumors after C-XRT. A specific LNR cutoff remains to be defined.