Oncotype DX genomic test could alter breast cancer treatment in Brazil

A Brazilian analysis presented at ASCO 2026 estimates that the Oncotype DX genomic test could alter chemotherapy recommendations for 43% of patients with early-stage breast cancer. The study, published in JCO Global Oncology, utilized modeling to determine how the test—which analyzes the activity of 16 tumor genes and 5 reference genes—might modify medical conduct for patients in Brazil's supplementary health sector.

These findings align with a previous 2021 prospective study involving 179 women at public hospitals in São Paulo. In that study, medical recommendations changed in 65% of cases after receiving test results. Most changes involved patients who were initially slated for chemotherapy but were instead transitioned to hormone therapy alone, resulting in a 66% relative reduction in chemotherapy recommendations.