Gene test reveals which women with breast cancer do not need chemotherapy

Research by Sparano et al published in the NEJM suggests that the gene test known as Oncotype DX may help women with early stage breast cancer avoid chemotherapy.

The authors performed a prospective trial involving women with hormone-receptor–positive, HER2–negative, axillary node–negative breast cancer with tumors of 1.1 to 5.0 cm in the greatest dimension (or 0.6 to 1.0 cm in the greatest dimension and intermediate or high tumor grade). The Oncotype DX assay of 21 genes was performed on the tumor tissue, and the results were used to calculate a score indicating the risk of breast-cancer recurrence; patients were assigned to receive endocrine therapy without chemotherapy if they had a recurrence score of 0 to 10 on a scale 1 to 100, indicating a very low risk of recurrence.

Of the 10,253 eligible women enrolled, 1626 women (15.9%) who had a recurrence score of 0 to 10 were assigned to receive endocrine therapy alone without chemotherapy. At 5 years, in this patient population, the rate of invasive disease–free survival was 93.8%, the lack of metastasis at a distant site was 99.3%, and the rate of overall survival was 98.0%.

The authors concluded that patients with hormone-receptor–positive, HER2-negative, axillary node–negative breast cancer, those with tumors that had a favorable gene-expression profile the test accurately identified the group of women whose cancers are likely to respond to hormone-blocking drugs and adding chemo would do little if any good while exposing them to side effects and other health risks.  The researchers found that patients who skipped chemo based on the test had a small chance of cancer recurrence at 5 years with endocrine therapy alone.