1596 Background: We characterized differences in presentation and survival, and identified predictors of survival, among women of varying race with lobular breast cancer. We also assessed if these trends were unique to ILC by comparing with invasive ductal carcinoma (IDC) and mixed invasive ductal-lobular carcinoma (IDLC). Methods: Using the SEER database, we performed a population-based retrospective cohort study of women diagnosed with ILC, IDC, and IDLC between 1998 and 2019. We collected race, age, marital status, and income. Clinical data included grade, size, laterality, clinical stage, receptor status, surgery type, chemotherapy, radiation, and breast-cancer-specific survival (BCSS). Differences between racial groups were assessed using Chi-square tests or one-way ANOVA. To identify predictors of survival, Cox-proportional hazard models were constructed. Statistical analyses were performed using SAS and P values < 0.05 were considered significant. Results: 38,769 women with ILC were identified, including 32,857 White, 2398 Black, 2352 Asian, and 1162 women of other race. Black women presented with higher-grade, advanced clinical stage, ER+ disease, N2-3 stage, and lower rates of unilateral/bilateral mastectomy than White women. Black women were more likely to not undergo surgery (7.13%), compared with White (4.25%) and Asian (4.04%) women ( P = .0001). Asian women were younger, had more ER-/PR- ILC, and received more chemotherapy. The five-year BCSS rates in Black, White, Asian, and women of other race were 91.5%, 94.2%, 93.7%, and 95.7%, respectively ( P< .0001). Predictors of worse survival include Black race (HR 1.32, P < .0001), ER-/PR- (HR 2.18, P< .0001), ER+/PR- (HR 1.52, P< .0001), and no surgery (HR 4.19, P < .0001). Radiotherapy was associated with improved survival (HR 0.82, P < .0001), while chemotherapy did not affect survival (HR 1.1, P= 0.0504). In comparing across breast cancer subtypes, Black women similarly present with higher grade tumors, advanced clinical stage, ER+ disease, and had higher rates of surgery omission in IDC and IDLC. However, ER-/PR- subtype was notably higher in ILC among Asian women compared with IDC, whereas Black women have higher rates of ER+/PR+ and ER-/PR- ILC. Black women had the lowest five-year BCSS rates across all breast cancer subtypes. Predictors of worse survival in IDC and IDLC include Black race and negative hormone receptor status, while radiation therapy was associated with improved survival. Conclusions: There are differences in clinical presentation of invasive lobular breast cancer according to race.Black women had more advanced disease, while Asian women were younger. Across all subtypes, overall survival for Black women at 5 years was worse compared to other racial groups. Our data provides insight into the complex interactions of race, clinical characteristics, and survival outcomes in lobular breast cancer, with implications for screening considerations.
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