Superiority of Pathologic Lymph Node Ratio over Positive Lymph Node Count in Operated Early-Stage Breast Cancer

AIM: In early-stage breast cancer, the axillary lymph nodes play a crucial role in determining the prognosis of the disease. The rate of lymph node involvement might be a more valuable prognostic factor than the number of positive lymph nodes. Therefore, we aimed to evaluate whether the lymph node ratio (LNR) is a superior prognostic indicator compared to the pathologic lymph node count in early-stage disease. METHODS: We included 3053 non-metastatic, lymph node-positive breast cancer patients who were treated and followed at 6 medical oncology centers in Türkiye between 2004–2018. Based on LNR, patients were classified into three risk groups: high (>0.65), intermediate (0.21–0.65), and low (≤0.20). RESULTS: Classification of patients according to the TNM8 system based on the number of positive lymph nodes revealed that pathologic lymph node count (pN)1 accounted for 49.0% (n = 1495), pN2 for 30.0% (n = 917), and pN3 for 21.0% (n = 641). Based on the LNR risk group, the low-risk group accounted for 45.4% (n = 1385), intermediate for 36.2% (n = 1105), and high for 18.4% (n = 563) of the total patients. For the entire patient cohort, the 5-and 10-year disease-free survival (DFS) were 93% and 67%, respectively, while overall survival (OS) rates were 95% and 75%, respectively. The median DFS for patients with N1, N2, and N3 disease was 149 months (94.2–203.7), 120.1 months (108.2–132.0), and 81.8 months (68.4–131.1), respectively (p < 0.001). The median DFS for the three LNR risk groups (low, intermediate, and high risk) was 148.9 months (95.3–202.6), 118.7 months (99.9–137.7), and 81.8 months (68.2– 95.3) respectively. Increasing LNR rate was an independent prognostic factor for DFS, according to multivariate analysis (p < 0.001). Furthermore, the median DFS was 133 months for pathologic N1 patients in the LNR intermediate-high risk group, while the median DFS was not reached in patients with LNR and the pN2 low risk group (p = 0.034). CONCLUSIONS: This study confirms the significance of LNR as a prognostic factor for DFS. The results show that in certain specific subgroups, LNR provides more information than pathologic lymph node counts.