Adjuvant endocrine therapy and chemoendocrine therapy appear to have similar efficacy in women with hormone receptor (HR)-positive, HER2-negative, axillary node-negative breast cancer whose 21-gene recurrence score (RS) is in the middle of the range, according to a study published in the New England Journal of Medicine. However, researchers found that some women aged 50 and younger derived some benefit from chemotherapy.

“Adjuvant endocrine therapy was noninferior to adjuvant chemotherapy plus endocrine therapy in women with hormone receptor-positive, HER2-negative, node-negative breast cancer and an Oncotype DX recurrence score of 11 to 25 who met clinical criteria for recommending or considering adjuvant chemotherapy,” explained study investigator J.A. Sparano, MD, professor of medicine & obstetrics, gynecology, and women’s health at the Albert Einstein College of Medicine, and associate chairman for clinical research in the Department of Oncology at Montefiore Medical Center, The Bronx, New York.

Dr Sparano said a subset of women aged 50 or younger with an RS of 21 to 25 derived some benefit from chemotherapy, with 7% fewer distant recurrences when chemotherapy was given. In addition, the study showed that distant recurrence rates at 9 years for those treated with endocrine therapy alone was 3% in women whose RS was less than 11, and 5% in women whose RS was 11 to 25.

THE STUDY

Oncotype DX is a gene expression assay used to quantify the risk of distant recurrence in women with HR-positive early breast cancer. The 21-gene assay score ranges from 0 to 100; the assay can successfully predict that women with a high RS will benefit from chemotherapy.However, the prediction value for women with a midrange RS has been controversial.

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Dr Sparano and colleagues conducted a prospective trial involving 10,273 women ages 18 to 75 years. Among the 9719 eligible patients with follow-up information, the researchers found that 69% (6711 women) had a midrange RS (11 to 25). These women were randomly assigned to chemoendocrine therapy or endocrine therapy alone. 

The researchers sought to determine the noninferiority of endocrine therapy alone for achieving invasive disease-free survival (ClinicalTrials.gov Identifier, NCT00310180). This end point was defined as “freedom from invasive disease recurrence, second primary cancer, or death.”