Abstract 4240: Breast cancer characteristics and survival among different Indigenous American communities in Peru

Abstract

Abstract Background: Breast cancer prognosis depends on stage at diagnosis and varies by intrinsic tumor subtype. In the US, the distribution of tumor subtypes has been shown to differ between racial/ethnic groups with African American and Latina women more likely to be diagnosed with the more aggressive “triple negative” breast cancer (TNBC) compared to Non-Latino White women. Latinos in the US originate from different countries with different cultures and ancestral genetic backgrounds, demonstrating the heterogeneity that exists. Information about the distribution of tumor subtypes in Latin American regions is limited. Methods: Data for these analyses come from The Peruvian National Cancer Institute . Includes clinical information for 303 patients diagnosed with breast cancer between 2010 and 2015 and who are members of Indigenous American communities. We analyzed women from different groups: the Quechuas (Group 1; N=223), Aimara (Group 2; N=9), Ashankinka/Nomatsigenga/Yenesha (Group 3; N=17), Awajun/Kichwa/Shawi/Shipibo-Konibo (Group 4; N=29) and other communities (Group 5; N=20). Some communities were combined based on previous literature describing their genealogical proximity. We compared tumor characteristics and survival between these groups using Fisher exact tests, T-tests, and a Cox Proportional Hazards model with predictors age at diagnosis, stage, tumor subtype, and treatment. Breast cancer subtype was defined as luminal A (ER/PR+/HER2-), luminal B (ER+/HER2+), HER2 overexpressing (ER/PR- HER2+) and triple negative (ER/PR- HER2-) based on immunohistochemistry. Results: Overall, tumors from the 303 Indigenous American women included in the present study were 37% luminal A, 20% luminal B, 23% HER2 overexpressing and 19% triple negative. Our analyses showed that women from group 1 were diagnosed at an older age (55 vs. 48-50, p<0.0001) and less frequently with TNBC compared to women from other groups (45% vs. 55-78%, p=0.06). Compared to group 1, women from the other groups a non-significant trend towards higher mortality (HR 1.5-1.9, p=0.272). In the full model, including age, stage, tumor subtype and treatment, the trend was no longer apparent. Whether the women had surgery had the strongest effect on survival (p=0.001) followed by stage (p=0.0012) and TNBC (p=0.0023). Conclusion: Differences in survival between the women of different indigenous communities with breast cancer in Peru are most likely due to differences in access to care. There could be environmental factors or subtle sub continental genetic differences influencing the risk of TNBC. However, the lower frequency of TNBC among the Quechuas could also be due to a reduced set of logistic barriers. The limited power of this study demonstrates the need for larger data sets for subgroup analysis in Latinas. The more we learn by analyzing diverse populations, the better equipped we will be to provide adequate care for all women. Citation Format: Lizeth I. Tamayo, Tatiana Vidaurre, Jeannie Navarro Vásquez, Sandro Casavilca, Jessica I. Aramburu, Monica Calderon, Daniel Cherry, Sikai Song, Garth H. Rauscher, Laura Fejerman. Breast cancer characteristics and survival among different Indigenous American communities in Peru [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4240.