Abstract PO5-17-10: PERFORMANCE AND OUTCOMES OF THE 70-GENES SIGNATURE (MAMMAPRINT™) IN A POPULATION WITH MIDDLE INCOME – REAL WORLD STUDY (AGEMA-BRA)

Abstract INTRODUCTION – Breast cancer remains the most frequent tumor in the female population and the fourth in mortality in the world population (GLOBOCAN 2020). With the aim of reducing mortality and at the same time de-escalating treatment, avoiding overtreatment, individualized therapy is increasingly being applied. The genomic signature of 70-genes, when stratifying patients into high and low risk of relapse, makes it possible to withdraw part of the cases of high clinical risk from chemotherapy treatment. However, the MINDACT study, which validated this signature, was carried out only in the European population, with no data on performance and outcomes in other populations with greater miscegenation. OBJECTIVE – To study the performance and outcomes of the 70-gene genomic signature (MammaPrint™) in a Brazilian population with a high ethnic miscegenation. METHODOLOGY – A retrospective cohort study was conducted in 953 women with breast cancer at high clinical risk, who underwent genomic analysis with the 70-gene platform (MammaPrint™), from January 2016 to December 2020. For the statistical evaluation, a descriptive analysis of the data with absolute and relative frequencies of the variables was performed. To verify the association between qualitative variables, the chi-square test was used. All analyzes were performed in the R 4.1.0 environment (R Core Team, 2021). Study approved by the Research Ethics Committee of the State University of Ponta Grossa (PR) - (CAAE: 12194219.4.0000.0105). RESULTS – The analysis of 955 cases from the AGEMABRA cohort (all at high clinical risk) showed 546 cases (57.2%) with low genomic risk and 409 cases (42.8%) with high genomic risk to MammaPrint™ (MP); when compared with data from the MINDACT study (46.2% low risk and 53.8% high risk) a significant difference was observed in the distribution for high and low risk in the two populations (p. 0.001). After excluding patients with missing data, 409 cases of low- and high-risk MP were studied. The variables regarding age group, tumor diameter, number of affected lymph nodes, hormone receptors and HER2 overexpression showed no significant difference; within this same analysis, the tumor grade showed a higher incidence of grade 1 in the population with low genomic risk (6.6%) compared to high risk (2.9%) and grade 3 in high risk (13%) compared to low risk (5%) with p. 0.001 (table 1). With an average follow-up of 40 months, the DMFS (disease metastatic free survival) found was 97.2%, being 97.8% for low risk and 96.2% for high risk (p.0.54). All patients with high-risk MP who progressed had used adjuvant chemotherapy, and all patients with low-risk MP who relapsed received only endocrine therapy. When compared to the MINDACT population, the AGEMA-BRA has more elderly patients, and smaller tumors with a lower histological grade (p.= 0.001). CONCLUSION – The analysis of the Brazilian population submitted to the 70-gene genomic signature showed a greater proportional number of tumors with low genomic risk than in the test approval study, favoring its application with the aim of de-escalating systemic treatment in this population. Despite the low rate of disease progression in the AGEMA-BRA study, probably determined by the population with the best prognosis disease and the short follow-up, recurrence was similar in the high and low genomic risk groups, demonstrating the adequate selection of systemic therapy following the results of the MP. An increase in the sample size and longer follow-up are necessary to confirm the results found. Table 1. Characteristics of patients and tumor according to risk (AGEMA-BRA) Citation Format: Fabio Mansani, Ruffo Freitas-Junior. PERFORMANCE AND OUTCOMES OF THE 70-GENES SIGNATURE (MAMMAPRINT™) IN A POPULATION WITH MIDDLE INCOME – REAL WORLD STUDY (AGEMA-BRA) abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-17-10.