A study of the impact of the 21-gene breast cancer assay on the use of adjuvant chemotherapy in women with breast cancer in a Mexican public hospital.

Abstract

The majority of breast cancer patients in Mexico are treated through the public health system and >80% receive adjuvant chemotherapy. The aim of this prospective study was to characterize the impact of the Oncotype DX assay on adjuvant therapy decision making and the confidence in those decisions amongst public sector physicians in Mexico. Ninety-eight consecutive patients with ER+, HER2-, stage I-IIIa, N0/N1-3 node-positive breast cancer from the Instituto Nacional de Cancerología were eligible for the study. The primary endpoint was the overall change in treatment recommendations after receiving the assay results. Of 96 patients, 48% received a chemohormonal therapy recommendation prior to testing. Following receipt of results, treatment decisions changed for 31/96 (32%) patients, including 17/62 (27%) node-negative patients and 14/34 (41%) node-positive patients. The proportion of patients with a chemotherapy-based recommendation decreased from 48% pre- to 34% post-assay (P=0.024). 92% of physicians agreed that they were more confident in their treatment recommendation after ordering the assay. These results suggest that use of the 21-gene assay in the Mexican public health system has a meaningful impact on adjuvant treatment recommendations that may reduce the overall use of chemotherapy.