In women with hormone-receptor-positive, HER2-negative, axillary node-negative breast cancer and a midrange recurrence score, adjuvant endocrine therapy and chemotherapy were similarly effective in a new study, indicating that it may be safe for many with early-stage disease to forgo the latter.
Researchers performed a prospective trial of 10,273 women 18 years of age and older who registered between April 7, 2006, and Oct. 6, 2001. Of these, 10,253 were eligible to participate in the trial, and 9,179 had follow-up information available. Among this group, 6,711 (69%) had a midrange recurrence score, defined as a score of 11 to 25, based on the 21-gene breast cancer assay; 1,619 (17%) had a recurrence score of 10 or lower; and 1,389 (14%) had a recurrence score of 26 or higher. While a high recurrence score predicts benefit from chemotherapy and a low score predicts a low risk of recurrence without chemotherapy, most patients fall in the middle range and the significance of their scores is uncertain, the study authors noted. Patients with midrange scores were randomly assigned to receive chemoendocrine therapy or endocrine therapy alone to determine noninferiority of the former for survival free of invasive disease recurrence, second primary cancer, or both. The study results were published June 3 by the New England Journal of Medicine.
At the final study analysis, 836 cases of invasive disease recurrence, second primary cancer, or death had occurred in the two treatment groups. When survival free of invasive disease was analyzed in the intention-to-treat population, endocrine therapy was found to be noninferior to chemoendocrine therapy (hazard ratio for invasive disease recurrence, second primary cancer, or both, 1.08; P=0.26). Rates of survival free of invasive disease were similar at nine years among the two treatment groups (83.3% vs. 84.3%, respectively). The two groups also had similar rates of freedom from distant disease recurrence (94.5% vs. 95.0%), freedom from recurrence at a distant or local-regional site (92.2% vs. 92.9%), and overall survival (93.9% vs. 93.8%). When different combinations of recurrence score and age were considered, the benefit of chemotherapy varied for survival free of invasive disease, with women 50 years of age or younger who had a score of 16 to 25 seeing some benefit, the authors noted.
“The results of our trial suggest that the 21-gene assay may identify up to 85% of women with early breast cancer who can be spared adjuvant chemotherapy, especially those who are older than 50 years of age and have a recurrence score of 25 or lower, as well as women 50 years of age or younger with a recurrence score of 15 or lower,” the authors wrote. “Ongoing clinical trials are obtaining additional information on the clinical usefulness of the 21-gene assay in women with hormone-receptor-positive breast cancer and positive axillary nodes and evaluating the clinical usefulness of the 50-gene assay in this context.”