Abstract PD9-10: Factors Associated with Early and Late Mortality in Invasive Lobular Carcinoma

Abstract Background: Breast cancer is the most common cancer and leading cause of cancer-related death in women. Invasive lobular carcinoma (ILC) is the second most common histological type of breast cancer after Invasive breast carcinoma of no special type (invasive ductal carcinoma [IDC]). ILC accounts for 10-15% of all breast cancer cases. Prior studies have suggested different patterns of short-term (<5 years) and long-term (>5 years) survival between ILC and IDC. However, comprehensive data on both outcomes is limited. The objective of our study was to identify the factors associated with early and late mortality in patients with ILC. Methods: We conducted a retrospective analysis using the National Cancer Database (NCDB) from 2006-2020. Inclusion criteria were female gender, age ≥ 18 years, lobular histology, breast cancer stage I-III and removal of breast cancer tumor and axillary lymph nodes. Our primary endpoint, overall survival (OS), was defined as time in months from the date of diagnosis until death. The short-term OS analysis evaluated survival from diagnosis until 5 years from diagnosis (censored data at 5 years). The long-term OS analysis evaluated those patients who were alive after 5 years from diagnosis. We used the Pearson X2 test to evaluate the relationship between categorical variables and the t test for continuous variables. Cox hazard regression models were used to identify factors associated with short-term (< 5 years) and long-term OS (> 5 years). Results: The analysis of short-term OS included 115,159 patients, most of them were Non-Hispanic White (81%) with a median age of 63 years. Most tumors were T1 (57%), N0 (71%), Hormone Receptor positive (ER+ 100%, PR+ 87%), HER2 negative (81%). 52,503 (46%) patients underwent mastectomy. The 5-year OS rate was 93%. Old age (Hazard Ratio [HR] 2.16; p <0.001), large tumor size (HR 1.97 p <0.001), axillary node involvement (HR 5.15; p <0.001), high grade (HR 1.59; p <0.001), and lymphovascular invasion (LVI) (HR 1.19; p <0.001) were associated with worse short-term OS; whereas mastectomy (HR 0.84, p <0.001), chemotherapy (HR 0.77; p <0.001), radiation (HR 0.6; p <0.001), PR positivity (HR 0.74; p <0.001) and endocrine therapy (ET) (HR 0.5; p <0.001) were associated with improved short-term OS. Among patients who had OncotypeDx testing (N= 3,800), compared to low-OncotypeDx recurrence score, those with high OncotypeDx recurrence score had worse short-term OS (HR 1.68; p <0.001), whereas the short-term OS was similar for those with intermediate OncotypeDx recurrence score (HR 0.67; p = 0.3). The analysis of long-term OS included 67,927 patients with a median age of 62 years. The 10-year OS rate for this cohort was 86%. Old age (HR 1.89; p <0.001), large tumor size (1.58; p <0.001), axillary nodal involvement (HR 4.38; p <0.001), high tumor grade (HR 1.37; p <0.001), and LVI (HR 1.12; p = 0.01) were associated with worse long-term OS; whereas mastectomy (HR 0.94; p = 0.04), chemotherapy (HR 0.81; p <0.001), radiation (HR 0.84; p <0.001), PR positivity and ET (HR 0.78; p <0.001) were associated with improved long-term OS. Among patients who had OncotypeDx testing (N= 18,339), compared to low OncotypeDx recurrence score, those with high OncotypeDx recurrence score had worse long-term OS (HR 1.8; p <0.001); whereas the long-term OS was similar for those with intermediate OncotypeDx recurrence score (HR 1.17; p = 0.08) Conclusion: Pathological characteristics such as size and nodal status are prognostic for short-term and long-term survival outcomes in ILC. Adjuvant chemotherapy and endocrine therapy improve short-term and long-term OS in ILC. High OncotypeDx recurrence score can identify patients with worse short-term and long-term OS. Our results highlight the prognostic value of pathological characteristics, genomic profiling, and adjuvant therapies in ILC beyond 5 years. Citation Format: J. Avila, X. Xue, A. Gyamfi, J. D. Anampa. Factors Associated with Early and Late Mortality in Invasive Lobular Carcinoma [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PD9-10.