De-escalation Of Endocrine Therapy In Early Hormone Receptor-positive Breast Cancer: When Is Local Treatment Enough?
*Roi Weiser, *Efstathia Polychronopoulou, Douglas S Tyler, V Suzanne Klimberg
UTMB, Galveston, TX
OBJECTIVE(S): De-escalation in breast cancer treatment has included surgery, radiation and chemotherapy and has often focused on older patient populations. Systemic endocrine therapy(ET) has yet to be de-escalated, though it carries serious side effects and decreased quality of life(QoL) over 5-10 years, regardless of its impact on local recurrence. We hypothesize the 21-gene recurrence score(RS) could identify subgroups of younger patients whose long-term survival is unaffected by adjuvant ET.
METHODS: The National Cancer Database identified women aged ≥50, with hormone receptor-positive, HER2-negative tumors, ≤3 cm in size, N0 and RS≤25, who underwent breast conserving surgery in 2010-2016. Kaplan-Meier and Cox proportional hazards models were used to identify association between treatment and overall survival(OS).
RESULTS: Of the 57,242 patients identified, 80.8% were 50-69 years old. 50,838(88.8%) patients received both ET and radiation, 3,217(5.6%) received ET, 2,282(4.0%) radiation, and 905(1.6%) neither. The 5-year OS of the entire cohort was 96.1%. After adjusting for all covariates, patients aged 50-69 with RS≤10 showed no clinically or statistically significant improvement in OS with the addition of ET to surgery, with or without radiation (Figure 1),(p=0.26). With RS 11-25, there was a significant improvement of OS with ET plus radiation (p=.0001).
CONCLUSIONS: Local treatment only, with de-escalation of long-term systemic ET for patients aged 50-69 with RS≤10, appears not to impact OS and should have an anticipated improvement in QoL. 
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