Adjuvant chemotherapy and survival outcomes in older women with HR+/HER2- breast cancer: a propensity score-matched retrospective cohort study using the SEER database.

ABSTRACT

OBJECTIVES: This study aimed to investigate the impact of adjuvant chemotherapy (ACT) on survival outcomes in older women with hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer (BC). DESIGN: A retrospective cohort study using data from the Surveillance, Epidemiology, and End Results database, which contains publicly available information from US cancer registries. SETTING AND PARTICIPANTS: The study included 45 762 older patients with BC aged over 65 years diagnosed between 2010 and 2015. METHODS: Patients were divided into two groups based on age 65-79 years and ≥80 years. Propensity score matching (PSM) was employed to balance clinicopathological characteristics between patients who received ACT and those who did not. Data analysis used the χ2 test and Kaplan-Meier method, with a subgroup analysis conducted to identify potential beneficiaries of ACT. OUTCOME MEASURES: Overall survival (OS) and cancer-specific survival (CSS). RESULTS: Due to clinicopathological characteristic imbalances between patients with BC aged 65-79 years and those aged ≥80 years, PSM was used to categorise the population into two groups for analysis: the 65-79 years age group (n=38 128) and the ≥80 years age group (n=7634). Among patients aged 65-79 years, Kaplan-Meier analysis post-PSM indicated that ACT was effective in improving OS (p<0.05, HR=0.80, 95% CI 0.73 to 0.88), particularly in those with advanced disease stages, but did not show a significant benefit in CSS (p=0.09, HR=1.13, 95% CI 0.98 to 1.31). Conversely, for patients aged ≥80 years, ACT did not demonstrate any improvement in OS (p=0.79, HR=1.04, 95% CI 0.79 to 1.36) or CSS (p=0.09, HR=1.46, 95% CI 0.69 to 2.26) after matching. Subgroup analysis also revealed no positive impact on OS and CSS. CONCLUSIONS: Patients with HR+/HER2- BC ≥80 years of age may be considered exempt from ACT because no benefits were found in terms of OS and CSS.