Abstract C074: Somatic mutations in the PIK3CA gene and its prognostic implications among Ethiopian breast cancer patients

Abstract

Abstract Purpose: The phosphatidylinositol-4, 5-bisphosphate 3-kinase (PIK3CA), catalytic subunit alpha (c) is frequently mutated in breast cancer (BC). Although the biological impact of PIK3CA mutations in BC has been studied in various parts of the world, limited data is available from sub-Saharan Africa. In this study, the frequency and the prognostic role of PIK3CA mutations were investigated among BC patients from Ethiopia. Methods: Formalin-fixed paraffin-embedded blocks and fresh frozen BC tissue samples were collected from patients newly diagnosed with BC. Histopathological evaluation was carried out using immunohistochemistry (IHC). PIK3CA mutation profiling was carried out using TaqMan® Mutation detection assay. The association between PIK3CA mutation status and clinical and histopathological features was evaluated. A survival regression (Cox’s model) was employed to assess the effect of PIK3CA mutation and other variables on survival. Results: The prevalence of the PIK3CA mutations was 20.4%. Mutation of the PIK3CA gene was mainly observed among younger (24%), early pT stage (19.4%), and G1/G2 tumors (22.3%). The proportion of mutation was 24.4%, 27.3% and 20% in ER+, PR+ and HER2- tumors, respectively. A marked difference was observed in the PIK3CA mutation frequency across the four major tumor subgroups. However, most of the mutated tumors were found among HR+/HER2− (24.1%) followed by HR+/HER2+ tumors (27.8%). In his study, only TNBC was negatively associated with the proportion of mutation in the PIK3CA gene (p-value= 0.02) in comparison to HR+/HER2- tumors. In multivariate Cox’s regression analysis, the advanced pT stage and HR−/HER2- IHC group independently predicted worse overall survival. However, PIK3CA mutation status was not associated with survival. Conclusions: The PIK3CA mutation was relatively high in HR+ tumors. Such relatively higher molecular aberrations among HR+ tumors can provide a benefit in choosing the best therapeutic option for breast cancer. Citation Format: Zelalem Desalegn Woldesonbet, Meron Yohannes, Adamu Addissie, Tamrat Abebe, Eva Johanna Kantelhardt, Martina Vetter. Somatic mutations in the PIK3CA gene and its prognostic implications among Ethiopian breast cancer patients [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr C074.