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Chemotherapy is the treatment of choice for approximately 50% of women diagnosed with breast cancer in the US; however, a recent study reveals that 70% of patients can possibly avoid chemotherapy for breast cancer and its unwanted side effects.
Women who are diagnosed with hormone receptor-positive breast cancer that has not yet spread to the lymph nodes usually undergo a 21-gene test, such as Oncotype DX. Using a 100-point scale, this test predicts the likelihood that cancer will return and whether or not chemotherapy is the best treatment option. High scores (26 and above) predict that there is a high chance that the cancer will return. Chemotherapy is considered the treatment of choice for these women. In contrast, low scores (10 and below) indicate a low risk of cancer recurrence and chemotherapy is not considered beneficial. Although the course of action is clear for women with high or low scores, the best treatment option for women with midrange scores (11-25) is not clear.
Is chemotherapy necessary for all breast cancer patients?
A team in the US investigated whether endocrine therapy (also known as hormone therapy) or chemotherapy was the best treatment option for women with early breast cancer with midrange scores on the 21-gene test. Their investigation, published recently in the New England Journal of Medicine, involved following 9,719 breast cancer patients aged 18-75 years for nine years. The women all had hormone-receptor-positive, human epidermal growth factor receptor-2 (HER2)-negative, axillary node-negative breast cancer, which made them eligible for the 21-gene test.
Two-thirds of women with early breast cancer have midrange scores
A total of 6,711 (69%) patients obtained midrange scores on the 21-gene test. Of the remaining patients, 1619 (17%) had a low score and 1389 (14%) a high score. As the team was interested in comparing the effectiveness of endocrine therapy with chemotherapy in patients with midrange scores, they randomly divided the 6,711 women with midrange scores into two treatment groups. One group of women received endocrine therapy alone and the other group received chemotherapy combined with endocrine therapy (known as chemoendocrine therapy).
Endocrine therapy is just as effective as chemotherapy
The team found that endocrine therapy alone was just as effective as chemoendocrine therapy for women with midrange scores. Nine years after receiving treatment, overall survival rates were similarly high for women in the endocrine only group (93.9%) and the chemoendocrine treatment groups (93.8%), and the majority of women were breast-cancer free in both groups (83.3% vs 84.3%, respectively). In addition, both endocrine and chemoendocrine therapies effectively prevented cancer recurring at distant sites (94.5% vs 95%, respectively).
The risk of cancer recurrence is associated with age
Despite these overall similarities between treatment options, the team found that the risk of cancer returning at a distant site was associated with age in women with midrange test results. Specifically, they found that recurrence rates were lower in women aged 50 years or younger following chemotherapy.
Chemotherapy is not necessary for most women
By setting out to determine the best treatment options for women diagnosed with early hormone-receptor-positive, human epidermal growth factor receptor-2 (HER2)-negative, axillary node-negative breast cancer, the team found that the use of chemotherapy for breast cancer hinges on a simple genomic test. Notably, they are confident that up to 70% of women, depending on their age, do not need to suffer the gruelling effects of chemotherapy if they obtain low to midrange results on the 21-gene test.
Written by Natasha Tetlow, PhD
Reference: Sparano JA, et al. Adjuvant chemotherapy guided by a 21-gene expression assay in breast cancer. NEJM. 2018. Available at, DOI: 10.1056/NEJMoa1804710.