Long-Term Survival Differences Between T1-2 Invasive Lobular Breast Cancer and Corresponding Ductal Carcinoma After Breast-Conserving Surgery: A Propensity-Scored Matched Longitudinal Cohort Study

Background: The role of histology subtype on the prognosis of T1-2 breast cancer patients receiving breast-conserving surgery (BCS) is not clear. Methods: The Surveillance, Epidemiology, and End Results (SEER) Program was used to compare overall survival, second primary cancer-free survival (CFS), and local recurrence risk (LR) for patients with invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC), both receiving BCS. Results: The study enrolled 196,688 patients with T1-2 disease receiving BCS, including 12,906 with ILC and 183,782 with IDC. Patients with IDC showed higher unadjusted annual rates of BCS than ILC. Five- and 10-year estimated survival rates were, respectively, 92.06% and 86.14% in ILC, compared to 90.50% and 85.26% in IDC (P =.12). In multivariable Cox regression, ILC patients showed advantage over IDC in overall survival (hazard ratio [HR] = 0.93, P =.001), whereas no significant differences in CFS (HR = 1.03, P =.33) and LR (HR = 1.17, P =.06) were found, which were consistent with results from matched cohort. In subgroup analyses, patients with grade III ILC had poorer CFS (HR = 1.23, P =.009) and higher LR (HR = 1.59, P =.01) than IDC. Conclusion: Histologic type is of prognostic importance in T1-2 patients receiving BCS, and surgeons should be cautious in performing BCS for individuals with grade III ILC.