Abstract 4184: Tumor and risk factor characteristics among breast cancer patients from different geographic regions in Peru
Authors: Zavala Valentina , Vidaurre Tatiana , Marker Katie , Vásquez Jeannie , Tamayo L , Florez Renzo , Casavilca Sandro , Calderon M , Abugattas J , Gómez H , Fuentes H , Monge-Pimentel C , Song S , Cherry D , Fejerman Laura 
Published: August 2019

There are few Latin American cohorts with available biospecimens that include women of high Indigenous American ancestry. The Peruvian population is characterized by a high degree of Native American (NA) ancestry, with this ancestral component varying between 56 to 100% on average, depending on the region. We have collected 1199 Peruvian samples from the Instituto Nacional de Enfermedades Neoplasicas in Lima. This cohort of patients represents a unique opportunity to study the molecular characteristics of breast cancer in the NA genetic and genomic background. Here we present a basic description of the women in the study and a comparison of tumor subtypes distribution and risk factor information of the patients by place of birth and residence.

We explored differences in tumor subtype distribution and risk factors in relation to place of birth or residence in the three main geographical region of Peru. To test differences in proportions we used Chi2 or Fisher-exact tests. To test differences in means for continuous variables we used ANOVA or t-tests. Genetic ancestry was estimated using genome wide genotypes and the program ADMIXTURE. Tumor subtypes were defined using the following criteria: ER+/PR+/HER2- as luminal A, ER+/PR+/HER2+ as luminal B, ER-/PR-/HER2+ as HER2+ and ER-/PR-/HER2- as triple negative.

Overall, the patients included in the study were relatively young (50 yrs, SD=11.0). The average number of full-term pregnancies was 3 (SD=1.8), the average age at first pregnancy 22 (SD=5.7) and age at menarche was 13 (SD=1.8). The tumor subtype distribution was 31% of Luminal B tumors, 24% luminal A, 12% HER2 and 12% triple negative and did not differ by place of birth or residence. We found that patients from the Coastal region were heavier and taller than those born in the Andean region (p&lt;0.005). Women born in the Coastal region had the lowest age at menarche and a lower number of full-term pregnancies (p&lt;0.0001). Similar trends were observed when we compared women by place of residence. Patients born in Lima, the Capital of Peru, smoke more (p&lt;0.05), were heavier, had lower age at menarche, lower number of full term pregnancies and were diagnosed at a younger age, compared to women born outside the city (p&lt;0.05). The distribution of NA genetic ancestry also varied by place of birth: patients born outside Lima had higher proportion of NA ancestry (78% SD=0.15 vs. 74%, SD=0.18, p&lt;0.05).

The distribution of tumor subtypes among women in the Peruvian breast cancer cohort did not differ by place of birth or residence. However, we found that for some breast cancer risk factors, exposures differed between women from different regions. Finally, given the relatively low observed values for reproductive and lifestyle related exposures and the high proportion of Indigenous American ancestry of Peruvian women, this cohort is likely to be particularly informative to study genetic predisposition to breast cancer.

Citation Format: Valentina Zavala, Tatiana Vidaurre, Katie Marker, Jeannie Vásquez, L Tamayo, Renzo Florez, Sandro Casavilca, M Calderon, J Abugattas, H Gómez, H Fuentes, C Monge-Pimentel, S Song, D Cherry, Laura Fejerman. Tumor and risk factor characteristics among breast cancer patients from different geographic regions in Peru [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4184.