There is a substantial amount of variability in chemotherapy delivery in breast cancer patients in current practice and gene expression profiling may account for a large percentage of this, according a study of 431 women (median age 58 years) with stage I-IIIA breast cancer. Recurrence score (RS) was low (<18), intermediate (18-30), and high (>30) in 56%, 37%, and 7% of 3 models which were compared using the likelihood ratio test and c-statistic to determine if the integration of RS resulted in better prediction of chemotherapy delivery. Chemotherapy was delivered to 30% of patients. Researchers found:

In the model integrating RS, intermediate or high RS was the most influential factor for chemotherapy delivery (OR, 7.87).

The integration of RS resulted in improved model fit and precision, indicated by the likelihood ratio test and an improved c-statistic (0.720 vs 0.856).

Citation: Rutter CE, Yao X, Mancini BR, et al. The influence of a 21-gene recurrence score assay on chemotherapy delivery in breast cancer. Clin Breast Cancer [Published online ahead of print September 18, 2015]. doi: 10.1016/j.clbc.2015.09.008.