The significance of microscopically positive lymph node margins (R1) following surgical resection for Stage III colon...

Microscopically positive resection margins (R1) are associated with poorer outcomes in colon cancer. While the sequalae of a positive margin related to the primary tumour (R1Tumour) are relatively well known, comparatively less is known when the positive margin pertains to a metastatic lymph node (R1LNM). The aim of this study is to confirm the significance and impact of R1LNM margins in colon cancer patients.

A retrospective, observational study of patients treated for American Joint Committee on Cancer Stage 3 colon cancer with potentially curative surgical intervention during a 10-year study period was performed. Patients were stratified into three groups (R0, R1Tumour, R1LNM). Outcomes measured were disease-specific survival (DSS), local recurrence-free survival (LRFS) and systemic recurrence-free survival (SRFS). Cox multivariable analysis and sensitivity analyses (time-stratified, competing-risk and propensity-matched analyses) were performed to determine the independent importance of R1LNM.

A total of 801 patients were included. The R1 resection rate was 6.6% and the R1LNM resection rate was 4.7%. Compared with R0 resection, R1LNM margins had significantly lower 5-year DSS [R1LNM 53.8% (95% CI 37.4%-77.3%) vs. R0 74.2%], LRFS [R1LNM 61% (95% CI 41.7%-89.1%) vs. R0 80.5%] and SRFS [R1LNM 39.5% (95% CI 24.2%-63.8%) vs. R0 70%]. R1LNM was not independently associated with the above outcomes following traditional, time-stratified and competing-risk multivariable analyses, nor following propensity matching.

R1LNM positivity may reflect other poor-prognosis variables, which themselves play a more substantial role in determining disease outcomes.