The overall sample size in all the risk strata defined according to recurrence score was driven by the need to include a sufficient number of patients with a score of 11 to 25 (midrange risk) in order to test the noninferiority of endocrine therapy alone versus chemotherapy plus endocrine therapy. At the fourth planned interim analysis held on March 20, 2015, the ECOG–ACRIN data and safety monitoring committee recommended that the results of the low-risk group be released and that follow-up in the randomized midrange-risk stratum and the nonrandomized high-risk stratum continue as planned. Although there was no specific enrollment goal for the low-risk group, the large sample provided the opportunity to estimate 5-year event rates accurately.
Statistical comparisons of baseline characteristics were calculated with the use of the chisquare test for categorical variables and the Wilcoxon test and Student’s t-test for continuous variables. Tumor size in the greatest dimension, histologic grade of the tumor, and expression of estrogen receptor, progesterone receptor, and HER2 were determined locally and reported by the participating site.
Event-free rates were estimated with the use of the Kaplan–Meier method, with confidence intervals computed with the use of the log–log transformation and Greenwood’s variance. The data-cutoff date for the results presented here was July 29, 2015.
Statistical comparisons of baseline characteristics were calculated with the use of the chisquare test for categorical variables and the Wilcoxon test and Student’s t-test for continuous variables. Tumor size in the greatest dimension, histologic grade of the tumor, and expression of estrogen receptor, progesterone receptor, and HER2 were determined locally and reported by the participating site.
Event-free rates were estimated with the use of the Kaplan–Meier method, with confidence intervals computed with the use of the log–log transformation and Greenwood’s variance. The data-cutoff date for the results presented here was July 29, 2015.
