Impact of the 21-gene recurrence score assay in adjuvant chemotherapy selection for node-negative, hormone receptor-positive breast cancer in the Chinese population

The 21-Gene Recurrence Score Assay has been intensively studied and recommended by major guidelines for treatment decision in early breast cancer. Its impact in adjuvant chemotherapy selection for Chinese population has not been revealed. The prospective part of this study enrolled consecutive node-negative, hormone receptor-positive patients who underwent 21-gene RS testing at Breast Surgery Department of PUMCH (n=134) between May 2012 and August 2013(21-gene RS group). Risk categories were assigned based on the RS and on standard clinicopathologic criteria according to St. Gallen and Adjuvant! Online. The chemotherapy selection and the oncologists' confidence in decision-making before and after RS testing were recorded. The retrospective part of this study compared the chemotherapy decision in the 21-gene RS group and a control group without RS testing (diagnosed between Jan 2011 and Apr 2012,n=170). A total of 304 patients were included in the analysis (134 21-gene RS group, 170 controls). Based on RS, 97 patients were classified as low risk, 29 patients as intermediate risk, and 8 patients as high risk. Tumor grade (P=0.002), PR expression (P<0.001) and Ki-67 index (P<0.001) were significantly different between the 3 risk cohorts.Comparing the St. Gallen guidelines and RS, there was a 41% concordance between risk groups. By using Adjuvant! Online, the correlation between the predicted BCSM and RS was nominal (r=0.10). A total of 29% 21-gene RS group patients changed their treatment decisions after RS testing (P<0.001, 95% CI, 0.18 to 0.49) with 6% (8/134) patients changing to receive chemotherapy besides endocrine therapy and 23% (31/134) changing to reject chemotherapy. After RS testing, more than one half of the oncologists increased their confidence level in treatment recommendation. In the control group, 67.6% (115/170) patients chose chemotherapy plus endocrine therapy. The chemotherapy percentage was much higher than that of 21-gene RS group (30/134, 22%). This is the first study to demonstrate a reduction in the use of adjuvant chemotherapy in Chinese woman with node-negative hormone receptor-positive breast cancer, based on use of the RS. The RS had an impact on the physicians' treatment decision-making.