Chemotherapy (CT) declination among patients with early-stage hormone receptor positive breast cancer (BC) and high Oncotype DX recurrence scores (RS).

525 Background: Among patients with hormone receptor positive, HER2-negative (HR+/HER2-) BC, the 21-gene Oncotype DX assay is both prognostic of recurrence risk and predictive of CT benefit. However, some patients decline CT despite their physician’s recommendations. We investigated the factors associated with CT declination and its impact on overall survival (OS) among patients with early-stage HR+/HER2- BC and high RS. Methods: Patients (≥18 years) diagnosed with HR+/HER2- BC from 2018-2021, with pathologic (p) T1-T3, pN0-N1 disease and RS >25, were identified in the National Cancer Database. Multivariable logistic regression was used to examine the factors associated with CT declination. Furthermore, multivariable Cox proportional hazards regression was used to evaluate the association between CT declination and OS based on a propensity score matched 1:5 cohort using year of diagnosis, age, race/ethnicity, pT and pN. Results: Among 23,416 patients with early-stage HR+/HER2- BC and RS >25, 74.3% were non-Hispanic White (NHW) and 12.1% were Black. Overall, 2601 (11.1%) patients declined CT despite physician recommendation (median RS of 30). Among those declining CT, 15.8% also declined endocrine therapy. On univariate analysis, CT declination was associated with older age, Black race and lobular histology. After adjustment, each unit increase in RS was associated with lower odds of CT declination (aOR=0.97; 95%CI 0.96–0.97). A more recent year of diagnosis was associated with lower odds of CT declination while older age and Black race (aOR=1.33; 95%CI 1.17–1.51) were associated with higher odds. Additionally, patients on Medicaid (aOR=1.66; 95%CI 1.40–1.97) and Medicare (aOR=1.29; 95%CI 1.12–1.48) had higher odds of declination compared to those on private insurance. Having pN1 disease was associated with lower odds of declination than pN0 disease (aOR=0.74; 95% 0.66–0.83). There was no association between comorbidity and declination. Notably, CT declination was associated with an increased risk of death after a median follow-up of 3 years (aHR=1.28; 95%CI 1.02–1.61) among 10,909 matched patients. Sensitivity analyses among patients with RS >30 showed similar results. Conclusions: Though prospective studies have demonstrated the benefit of CT among patients with high RS, 11% of patients declined CT. We observed a decrease in CT declination over time, as well as with increasing RS. Of note, Black patients, and those on Medicaid or Medicare were more likely to decline chemotherapy. CT declination was associated with worse OS. While the reasons for treatment declination are multifactorial, research is needed to understand the underlying disparities and work toward improving cancer care delivery.