Chemotherapy refusal and subsequent survival in healthy older women with high genomic risk estrogen receptor-positive breast cancer.

Background: Patients with estrogen receptor (ER)-positive, HER2-negative breast cancer (BC), and high-risk 21-gene recurrence score (RS) results benefit from chemotherapy. We evaluated chemotherapy refusal and survival in healthy older women with high-RS, ER-positive BC.

Methods: Retrospective review of the National Cancer Database (2010-2017) identified women ≥ 65 years of age, with ER-positive, HER2-negative, high-RS (≥ 26) BC. Patients with Charlson Comorbidity Index ≥ 1, stage III/IV disease, or incomplete data were excluded. Women were compared by chemotherapy receipt or refusal using the Cochrane-Armitage test, multivariable logistical regression modeling, the Kaplan-Meier method, and Cox's proportional hazards modeling.

Results: 6827 women met study criteria: 5449 (80%) received chemotherapy and 1378 (20%) refused. Compared to women who received chemotherapy, women who refused were older (71 vs 69 years), were diagnosed more recently (2014-2017, 67% vs 61%), and received radiation less frequently (67% vs 71%) (p ≤ 0.05). Refusal was associated with decreased 5-year OS for women 65-74 (92% vs 95%) and 75-79 (85% vs 92%) (p ≤ 0.05), but not for women ≥ 80 years old (84% vs 91%; p = 0.07). On multivariable analysis, hazard of death increased with refusal overall (HR 1.12, 95% CI 1.04-1.2); but, when stratified by age, was not increased for women ≥ 80 years (HR 1.10, 95% CI 0.80-1.51).

Conclusions: Among healthy women with high-RS, ER-positive BC, chemotherapy refusal was associated with decreased OS for women ages 65-79, but did not impact the OS of women ≥ 80 years old. Genomic testing may have limited utility in this population, warranting prudent shared decision-making and further study.