Breast cancer and molecular testing in Brazil.

Abstract

e13602 Background: Breast cancer is a common malignancy among women worldwide. Regardless of the economic status of a country, breast cancer poses a burden in prevention, diagnosis and treatment.Accurate pathologic and molecular diagnosis of high quality in breast cancer is a challenge in low- and middle-income countries (LMIC). The two most important aspects needed are the hormonal and epidermal growth factor receptor 2 (HER2) status as they are used as prognostic factor and as predictive biomarker for treatment. The most commonly used tests for assessing HER2 status are immunohistochemistry (IHC) assays for HER2 protein expression and fluorescence in situ hybridization (FISH) for HER2 gene amplification.In this study, we evaluated the hormonal and HER2 status of women with breast cancer and the need for FISH in HER2+++. Methods: We retrospectively reviewed the database of the Hospital Evangelico de Cachoeiro de Itapemirim, a regional cancer center from the south of Espirito Santo State – Brazil.The period covered in the study was from 01/08/2019 to 01/08/2020. We analyzed all new cases of invasive breast cancer diagnosed by IHC for the estrogen (ER), progesterone (PR) and HER2 receptors. All the HER 2++ and HER2 +++ were tested by FISH. We had during this period 152 newly diagnosed cases, 11 patients were excluded due to missing data. Results: The 141 cases were separated into four categories by hormonal status: 109 ER+PR+ (77,3%), 9 ER+PR− (6,4%), 2 ER−PR+ (1,4%) and 21 ER−PR− (14,9%). When these results were associated to HER 2 status we found 11 (7,8 %) triple negative breast cancer (TNBC) , 26 (18,43%) HER2 ++ and 23 (16,31%) HER 2+++. The HER2++ were tested by FISH and 8 (30,7%,) were found positive, 10 (38,6%) negative and 8(30,7%)indeterminate. Among the HER 2 +++ tested by FISH we found 15 (65,3 %) positive and 8 (34,7 %) indeterminate. Conclusions: Our study demonstrated a lower incidence of TNBC and higher incidence of hormone-receptor positive cases as compared with other institutions. Different from other countries, all HER 2++ and HER2+++ in Brazil need to go to molecular testing. Altough trastuzumab is available in the public Brazilian Health System (SUS) for HER 2 positive women, diagnosis with IHC alone is not permitted and there is a need for molecular testing confirmation. Therefore, the most troublesome data in this study was that 34,7% of HER 2+++ had indeterminate FISH results, in these cases SUS does not offer traztuzumab. Newer guidelines allow the use of IHC only in HER2 +++ . We consider important for SUS to review the recommendation for need of molecular testing for all HER2 +++ so this will avoid subtreating women in Brazil