Impact of the 21-gene recurrence score testing on chemotherapy selection and clinical outcomes in T3N0 luminal breast cancer.

Background: The role of 21-gene recurrence score (RS) testing on chemotherapy decision-making and survival outcomes for T3N0 luminal breast cancer (BC) remains unclear. This study aimed to investigate the effect of RS testing in chemotherapy selection and prognosis in these patients.

Research design and methods: Patients diagnosed with T3N0 luminal BC were included from the Surveillance, Epidemiology, and End Results Oncotype database. The likelihood of undergoing chemotherapy was analyzed using the chi-square test and binomial logistic regression. Survival analysis used Kaplan-Meier method and multivariate Cox proportional hazards models.

Results: Of the 3186 patients, 852 (26.7%) underwent RS testing. Those who had RS testing demonstrated a lower probability of chemotherapy receipt than those without RS testing (27.0% vs. 47.5%, p < 0.001). Higher RS correlated with increased the probabilities of chemotherapy receipt. The probabilities of chemotherapy for low-risk, intermediate-risk, and high-risk were 9.8%, 26.7%, and 60.6%, respectively (p < 0.001). RS testing independently improved breast cancer-specific survival (p < 0.001) and overall survival (p < 0.001). In the high-risk cohort, chemotherapy administration was associated with improved overall survival than those who did not (p = 0.038).

Conclusions: Our study highlights the significant role of RS testing in guiding treatment decisions and improving survival outcomes for patients with T3N0 luminal BC.