Studies Compare Long-Term Survival of Two Lymphadenectomy Techniques in Right-Sided Colon Cancer

RELARC Study Group. Long-Term Survival on Extent of Lymphadenectomy for Right-Sided Colon Cancer: Five-Year Follow-Up Results of a Randomized Controlled Trial (RELARC Trial). Li K, Li H, Wu A, et al. Ann Surg. September 2025.

The RELARC trial provides valuable long-term data comparing complete mesocolic excision (CME) with standard D2 lymphadenectomy for right-sided colon cancer. After 5 years of follow-up in nearly 1,000 patients, the study identifies specific subgroups that may benefit from CME over standard lymphadenectomy by examining their overall survival (OS) and cancer-specific survival (CSS).

Specifically, patients with pathological N2 lymph node involvement (OS: HR: 0.25, 95% CI: 0.11-0.57, P=0.001; CSS: HR: 0.25, 95% CI: 0.11-0.57, P=0.001) or those exhibiting lymphovascular invasion (LVI) (OS: HR: 0.34, 95% CI: 0.17-0.70; interaction P=0.009; CSS: HR: 0.32, 95% CI: 0.15-0.67, P=0.008) showed significantly improved 5-year OS and CSS with CME. 

However, for most patients, and if the study group is looked at as a whole, there is no difference in survival between the two surgical techniques (OS: HR: 0.74, 95%CI: 0.51-1.07, P=0.105). This suggests that the oncologic benefit of more extensive lymphadenectomy may be confined to patients with higher nodal burden or aggressive histologic features, where central node involvement is more prevalent. 

This creates a surgical dilemma, given LVI and extent of nodal disease is most often unknown preoperatively. Given these findings, surgeons should balance the technical demands and potential morbidity of CME against its selective survival advantages, applying individualized judgment based on tumor stage and evidence of nodal involvement in imaging.