In patients with breast cancer with a recurrence score based on a 21-gene expression assay of 11 to 25, outcomes were similar whether chemotherapy was used or not.
In patients with hormone receptor–positive, HER2-negative, lymph node–negative breast cancer with a recurrence score (RS) based on a 21-gene expression assay of 11 to 25, outcomes were similar whether chemotherapy was used or not used, according to a retrospective analysis. However, the study’s limited follow-up means a benefit from chemotherapy in these patients cannot be ruled out.
The Oncotype DX 21-gene expression assay is the most commonly used test of this kind in breast cancer in the United States. It offers an RS, and previous research has shown that patients with an RS below 11 fare very well when treated with endocrine therapy alone. “To our knowledge, it is unknown whether chemotherapy provides any additional benefit in outcomes in patients with hormone receptor–positive, HER2-negative, lymph node–negative, early-stage breast cancer with an RS of 11 to 25 who are treated with endocrine therapy,” wrote study authors led by Carlos H. Barcenas, MD, MSc, of the University of Texas MD Anderson Cancer Center in Houston.
This study included 1,424 patients who underwent the gene expression assay. Among these patients, 297 had an RS of 0 to 10 (21%), 894 had an RS of 11 to 25 (63%), and 233 had an RS of > 25 (16%). In each of these subgroups, 1.7%, 15%, and 73.4%, respectively, received chemotherapy. Results of the study were published in Cancer.
A total of 549 women who were diagnosed between 2005 and 2011 with an RS of 11 to 25 were categorized by receipt of chemotherapy. After a median follow-up of 58 months, there were 41 “outcome events,” including 10 distant recurrences, 3 local recurrences, 7 deaths, 11 second primary breast cancers, and 10 primary cancers at other sites.
There were no differences between patients who did and did not receive chemotherapy in any of the following four outcome measures. The hazard ratio (HR) for chemotherapy’s effect on invasive disease–free survival was 1.64 (95% CI, 0.73–3.71; P = .233). For recurrence-free survival, the HR was 1.46 (95% CI, 0.41–5.23; P = .564), and for distant recurrence–free survival it was 1.25 (95% CI, 0.32–4.92; P = .746). For overall survival, the HR was 2.19 (95% CI, 0.44–11.0; P = .340).
The authors noted that the results are limited by the low overall number of events, as well as the relatively short follow-up period. “A benefit from chemotherapy in this group cannot be ruled out because a longer follow-up is required to observe future events,” they concluded.