Breast cancer has the highest incidence and mortality rate of any female cancer (1), and in 2001, a National Institutes of Health-sponsored panel recommended that adjuvant chemotherapy should be offered to the majority of women with localized disease, regardless of variables such as hormone receptor status (2). However, it’s generally accepted that many with estrogen-receptor-positive breast cancer respond well to adjuvant endocrine therapy alone, which means that a substantial number of women could be getting needlessly overtreated under current guidelines. This might not be the case for long though. According to a recent study published in the New England Journal of Medicine (3), a gene expression assay could help oncologists identify those women who can safely forgo chemotherapy, without a high risk of cancer recurrence. The test analyzes the expression of 21 genes, including locations associated with cancer proliferation (such as Ki67) and invasion (MMP11) on a tumor sample, and assigns the tumor a score between 0 and 100 – the lower the score, the lower the chance of cancer recurrence following treatment with endocrine therapy.
In a multicenter validation study of over 10,000 women with hormone-receptor-positive, HER2-negative, axillary node-negative breast cancer, those with scores of 10 or lower did not receive chemo, and five years on, there was less than a 2 percent risk of metastasis, and overall patient survival of 98 percent. Women with a score of 11 to 25 – which accounted for nearly 68 percent of trial participants – were randomly assigned to either chemo and endocrine therapy or endocrine therapy alone; follow-up assessments are currently underway. It will be very interesting to see the impact on survival in these two groups. If endocrine therapy proves sufficiently effective in this study, it could substantially impact breast cancer treatment and potentially kickstart an update to the 2001 recommendations.
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References
- A Jemal, et al., “Global patterns of cancer incidence and mortality rates and trends”, Cancer Epidemiol Biomarkers Prev, 19, 1893–1907 (2010). PMID: 20647400. JS Abrams, “Adjuvant therapy for breast cancer – results from the USA consensus conference”, Breast Cancer, 8, 298–304 (2001). PMID: 11791121. JA Sparano, et al., “Prospective validation of a 21-gene expression assay in breast cancer”, N Engl J Med, [Epub ahead of print] (2015). PMID: 26412349.