Abstract B79: Breast cancer characteristics and survival among Indigenous American women from Peru
Authors: Tamayo Lizeth I. , Vidaurre Tatiana , Vasquez Jeannie Navarro , Casavilca Sandro , Palomino Jessica Ivonne Aramburu , Calderon Monica , Rauscher Garth H. , Fejerman Laura 
Published: February 2019

Background: Breast cancer prognosis depends on stage at diagnosis and varies by intrinsic tumor subtype. In the US, the distribution of intrinsic subtypes has been shown to differ between racial/ethnic groups with African American and Hispanic/Latina women more likely to be diagnosed with the more aggressive triple-negative breast cancer (TNBC) lacking expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), compared to non-Hispanic/Latino White women. Hispanics/Latinos in the US are a heterogeneous group originating from different countries with different cultures and ancestral backgrounds. Information about the distribution of tumor subtypes in Latin American regions is lacking.

Methods: Data for these analyses come from the Instituto Nacional de Enfermedades Neoplásicas (the Peruvian National Cancer Institute), which diagnoses and treats ~20% of all breast cancers diagnosed in Peru. We have abstracted data from clinical records for 303 patients diagnosed with breast cancer between 2010 and 2015 and who are members of Indigenous American communities from the Andean Mountain region (N=232) or the Amazonian region (N=71). We compared tumor characteristics and survival between the two groups. Comparisons between the two regions were conducted using chi-squared tests, as well as a t-test for age at diagnosis. 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. Survival analyses were conducted using a Cox proportional hazards model and included region, age at diagnosis, stage, and tumor subtype as predictors.

Results: Overall, tumors from the 303 Indigenous American women from Peru 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 the Amazonian region were diagnosed at a younger age (50 vs. 55 mean age at diagnosis, P value =0.001), later stage (61% vs. 48% stage III or IV, P value=0.06), and more frequently with triple-negative tumors compared to women from the Mountain region (31% vs. 17%, P value =0.013). Women from the Amazonian region had a 70% higher mortality hazard than the women from the Mountain region in a model adjusted by age at diagnosis (hazard ratio 1.73, 95%CI 1.06-2.86, p=0.027). In the full model including stage and tumor subtype, the difference in the mortality hazard was no longer statistically significant (HR 1.20, 95%CI 0.71-2.03, p=0.493).

Conclusion: Differences in tumor characteristics and survival between Indigenous American women from the Amazonian and Mountain Range regions in Peru could be due to variation in genetic predisposition to particular subtypes of the disease, variation in environmental exposures, as well as to differences in cancer awareness and access to care between the different groups. The more we learn by analyzing diverse populations and subpopulations and revealing heterogeneity within Latin American women, the better equipped we will be to provide adequate care for all women.

Citation Format: Lizeth I. Tamayo, Tatiana Vidaurre, Jeannie Navarro Vasquez, Sandro Casavilca, Jessica Ivonne Aramburu Palomino, Monica Calderon, Garth H. Rauscher, Laura Fejerman. Breast cancer characteristics and survival among Indigenous American women from Peru [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr B79.