Prognostic value of axillary lymph node metastases in invasive lobular breast carcinoma

Background: Axillary lymph node involvement is a well-established prognostic factor for recurrence in breast cancer, specifically the number of nodes affected and the ratio of the number of affected nodes to the number of harvested nodes for non-specific invasive breast cancer (invasive ductal carcinoma). However, there is limited information on the impact of lymph node involvement in the case of invasive lobular carcinoma. Objectives: our study aimed to evaluate the prognostic impact of lymph node involvement on overall survival and distant metastatic-free survival according to the number of nodes affected and the ratio of positive nodes (LNR) for patients managed for invasive lobular carcinoma. Methods: This is a monocentre, comparative, observational study of patients managed for invasive lobular carcinoma at the Gynaecology Department of the University Hospital Center of Tours between January 1, 2007 and December 31, 2018. The LNR cut-off values used were: low risk if LNR <= 0.2; intermediate risk if LNR > 0.2 and <= 0.65, and high risk for LNR >0.659. Results: Our study demonstrated a significant difference in overall survival and distant metastasis free survival (p < 0.0001). The 5-years Overall survival was 94 % for N0 patients, 92.4 % for low-risk patients, 85.6 % for intermediate-risk patients and 58.5 % for high-risk patients. The 5-year distant metastasis-free survival was 98.2 % for N0 patients, 95.9 % for low-risk patients, 80.1 % for intermediate-risk patients, and 60.3 % for high-risk patients. Multivariate analysis identified age, invasive lobular histologic type, presence of clinical inflammation, and intermediate and high risk classes of LNR ratio as independent factors affecting overall survival. For metastatic-free survival, the presence of clinical inflammation, the presence of LVSI and the low, intermediate, or high-risk classes of LNR ratio were identified as independent factors. However, age and invasive lobular histologic type did not appear to be independent factors affecting metastatic-free survival. Conclusion: Our study highlights the significant prognostic impact of lymph node involvement in patients with invasive lobular carcinoma. The LNR ratio can be used as a reliable predictor of overall survival and metastatic-free survival in these patients.