Evaluation of whether adjuvant chemotherapy can be safely omitted for older female patients with ER-positive, HER2-negative N1 breast cancer: a study based on the SEER database.

backgroundThis study evaluated the trends and practice patterns associated with adjuvant chemotherapy (CT) use for patients aged ≥70 years with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) N1 (1-3 positive lymph nodes) breast cancer (BC). Furthermore, the relationship between adjuvant CT and survival in this set of patients was determined.

methodsThe Surveillance, Epidemiology, and End Results (SEER) database was used to identify 6,711 women with ER+, HER2- N1 BC who were aged ≥70 years between 2010 and 2015. Demographic, clinical, and pathological predictors of CT use were identified using logistic regression. Multivariable Cox regression was used to identify variables that correlated with overall survival (OS), before and after propensity score matching (PSM).

resultsYounger age at diagnosis, other histological types, higher tumor grade, larger tumor size, breast reconstruction surgery, progesterone receptor-negative (PR-), and increased nodal involvement were associated with an increased probability of receiving CT. CT use was associated with improved 5-year OS, both before and after PSM [hazard ratio (HR): 0.66, 95% confidence interval (CI): 0.58-0.75 and HR: 0.81, 95% CI: 0.68-0.96, respectively]. The exploratory subgroup analysis showed that although the benefit of CT was significant in the grade III subgroup, it was not significant in the grades I-II subgroups.

conclusionsAdjuvant CT improved 5-year OS in patients with ER+, HER2- N1 BC who were aged ≥70 years; however, the benefit of CT was more significant in the grade III subgroup than in the grades I-II subgroups.