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.