Prognostic impact of lymph node ratio outperforms positive lymph nodes and lymph nodes harvested: A time-dependent analysis in mismatch repair-proficient and -deficient colorectal cancers I. Zlobec * , E. Karamitopoulou, L. Terracciano, D. Inderbitzin, A. Lugli * University of Berne, Inst. of Pathology, Bern, Switzerland Objective: We compare the prognostic strength of the lymph node ratio (LNR), positive lymph nodes (+LNs) and collected lymph nodes (LNcoll) using a time-dependent analysis in colorectal cancer patients stratified by mismatch repair (MMR) status. Method: 580 stage III-IV patients were included. Multivariable Cox regression analysis and time-dependent receiver operating characteristic (tROC) curve analysis were performed. The Area under the Curve (AUC) over time was compared for the three features. Results were validated on a second cohort of 105 stage III-IV patients. Results: The AUC for the LNR was 0.71 and outperformed + LNs and LNcoll by 10-15 % in both MMR-proficient and -deficient cancers. LNR and + LNs were both significant (p <0.0001) in multivariable analysis but the effect was considerably stronger for the LNR [LNR: HR=5.18 (95 % CI: 3.5-7.6); +LNs=1.06 (95 % CI: 1.04-1.08)]. Similar results were obtained for patients with >12 LNcoll. An optimal cutoff score for LNR = 0.231 was validated on the second cohort (p<0.001). Conclusion: The LNR outperforms the + LNs and LNcoll even in patients with >12 LNcoll. Its clinical value is not confounded by MMR status. A cut-of score of 0.231 may best stratify patients into prognostic subgroups and could be a basis for the future prospective analysis of the LNR.