The Prognostic Value of Lymph Node Ratio in Stage III Colorectal Cancer

Background: Stage III colorectal cancer (CRC) is prognostically heterogeneous. The lymph node ratio (LNR), defined as metastatic lymph nodes divided by examined lymph nodes, may provide risk information complementary to conventional nodal assessment. We evaluated the association of LNR with overall survival (OS) and disease-free survival (DFS), and explored its relationship with recorded pathological N (pN) category. Methods: This retrospective cohort included 103 patients with stage III CRC treated by upfront resection with lymphadenectomy at Rizgary Teaching Hospital/Rizgary Oncology Center between September 2013 and January 2025. The primary LNR categorisation was <0.20 versus >=0.20. Time-to-event analyses included 101 patients with usable follow-up. OS was time to all-cause death; DFS was redefined as time to first documented recurrence or death. Kaplan-Meier, log-rank, and parsimonious Cox models were used. Sensitivity analyses assessed LNR cut-offs of 0.10 and 0.25 and continuous LNR. An exploratory complete-case model included both LNR and recorded pN category. Results: Baseline LNR was <0.20 in 50 patients and >=0.20 in 53. Among 101 patients with outcome follow-up, 27 deaths occurred. OS differed by LNR group (log-rank p=0.006); 3-year Kaplan-Meier OS was 90.3% versus 59.8% and 5-year OS was 80.1% versus 48.4% for low versus high LNR. In a parsimonious model adjusted for adjuvant treatment, high LNR was associated with mortality (HR 3.24, 95% CI 1.37-7.70; p=0.008). Composite DFS also differed (log-rank p=0.007; adjusted HR 2.54, 95% CI 1.24-5.19; p=0.011). Results were similar at the 0.25 cut-off but weaker at 0.10. In 70 patients with recorded pN1/pN2 category, the LNR estimate was imprecise after inclusion of pN (HR 1.39, 95% CI 0.31-6.20; p=0.667). Conclusions: Higher LNR was associated with poorer OS and DFS in this cohort. However, the small event count, incomplete pN data, and attenuation in the exploratory pN-adjusted analysis do not establish that LNR provides independent incremental prognostic value beyond conventional N staging. Larger prospective, multicentre studies are required.