Abstract PO-217: Race and metastatic behavior of breast cancer subtypes

Abstract

Abstract Introduction: Racial/ethnic differences exist in early-stage breast cancer, but less is known about whether there are racial differences in metastatic sites of breast cancer. Thus, we examined racial/ethnic differences in metastatic behavior of de novo metastatic breast cancer (MBC). Methods: We identified 28,072 adult women (63.9% non-Hispanic White [NHW], 16.6% non-Hispanic Black [NHB], 7.7% non-Hispanic Asian or Pacific Islander [API], 11.8% Hispanic) diagnosed with de novo MBC in the Surveillance, Epidemiology and End Results between 2010 and 2018. Sites of distant metastasis included bone, lung, liver, and brain. Age-standardized incidence rates and incidence rate ratios (IRRs) were calculated. Logistic regressions were used to estimate the multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Results: NHBs had the highest incidence of MBC (13.2 per 100,000). Bone is the most common site of distant metastasis (63.1%). The risks of developing distant metastases to different sites varied by race/ethnicity. Compared with NHW women, NHB women had higher risks of bone (IRR=1.37, 95% CI 1.32-1.43), lung (IRR=1.91, 95% CI 1.80-2.03), liver (IRR=1.62, 95% CI 1.52-1.73), and brain (IRR=1.72, 95% CI 1.51-1.94) metastases. API and Hispanic women had lower risks of bone, lung, and liver metastases than NHW women, and API women also had a lower risk of brain metastasis. In women with hormone receptor-positive and HER2-negative MBC, NHBs, Hispanics, and APIs had a higher risk of lung metastasis and a lower risk of bone metastasis than NHWs after adjusting for age, year of diagnosis, marital status, tumor histology and grade. In women with hormone receptor-positive and HER2-positive MBC, NHB race was related to a higher risk of lung metastasis, and API race to a lower risk of bone metastasis. Hispanics with triple-negative MBC had a lower risk of liver metastasis than their NHW counterparts. A lower risk of liver metastasis was also observed in APIs and Hispanics with hormone receptor-negative and HER2-positive MBC than their NHW counterparts. Conclusions: The association of race and ethnicity with the risk of MBC differed by metastatic sites and tumor subtypes. Propensity to lung metastasis in NHB women with hormone receptor-positive MBC, Hispanics and APIs with hormone receptor-positive and HER2-negative MBC suggests the importance of preventive efforts targeting lung metastasis in these vulnerable patients. Citation Format: Yunan Han, Graham A. Colditz, Min Lian, Ying Liu. Race and metastatic behavior of breast cancer subtypes [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-217.