Lower survival after right-sided versus left-sided colon cancers: Is an extended lymphadenectomy the answer?

Introduction: Tumour location may affect oncologic outcomes for colon adenocarcinoma due to different levels of vascular ligation and nodal harvest, but the data are equivocal. The objective of this study is to determine the effect of tumor location and lymph node yield on overall survival(OS) in stage I-III colon adenocarcinoma.

Methods: The 2004-2014 National Cancer Database was queried for colectomies for non-metastatic colon adenocarcinoma, excluding transverse colon and rectal cancer. Patients were grouped based on left/right tumor location. Main outcome measure was 5-year OS. Propensity score matching created balanced cohorts. Multilevel survival analysis determined the independent effect of tumor location and nodal harvest on OS.

Results: There were 504,958 patients (273,198 right; 231,760 left) in the entire cohort: 26.4% stage-I, 37.3% stage-II, and 36.3% stage-III (equal distribution left/right). After 1:1 matching(n = 297,080), right cancers were associated with worse 5-year overall survival for stage-II (66% vs. 70%, p < 0.001) and -III (56% vs. 60%, p < 0.001) despite similar nodal harvest and proportion receiving systemic therapy. On multivariate analysis, right-sided cancers (HR 1.12, 95%CI 1.06-1.19) had worse OS, independent of stage and nodal harvest. Nodal harvest ≥22 nodes had the highest OS (HR 0.71, 95%CI 0.68-0.75). There was an interaction between right-sided cancer and >22 lymph node harvest towards increased survival (HR 0.86, 95%CI 0.80-0.92).

Conclusions: Right-sided cancers are associated with worse oncologic outcomes compared to left-sided tumors but a higher lymph node yield improves survival. These data provide indirect evidence for a higher lymphatic harvest to improve survival.