The necessity of adjuvant chemotherapy in young patients with T1N0M0 breast cancer: a population-based study

Chemotherapy clearly adversely affects fertility in women of childbearing age. But it is not yet clear whether chemotherapy at the expense of fertility can benefit younger patients with early-stage breast cancer. We conducted a retrospective cohort study utilizing the Surveillance, Epidemiology, and End Results database and the Shanghai Jiao Tong University Breast Cancer Data Base spanning from 2010 to 2020 to investigate early-stage breast malignant carcinoma in patients aged between 20 and 39 years. To address covariate imbalance, propensity score matching (PSM) was employed with a ratio of 1:1 and caliper set at 0.02 standard deviation of propensity score. Univariate and multivariate analyses were performed to evaluate the impact of chemotherapy on both breast cancer-specific survival (BCSS) and overall survival (OS). We identified a total of 6265 patients with complete information about breast cancer. Among them, 3855 patients received chemotherapy. Following successful PSM, we obtained a matched cohort comprising 3038 patients where the characteristics between the two groups were balanced except for race. Kaplan-Meier survival analysis revealed no significant differences in BCSS (P = 0.183) and OS (P = 0.295) between the chemotherapy group and no-chemotherapy group. Similarly, in matched dataset. multivariate COX analysis revealed that chemotherapy did not significantly reduce the risk of BCSS (HR 1.332; 95% CI [0.865-2.051], P = 0.193) and OS (HR 1.225; 95% CI [0.818-1.833], P = 0.324). The chemotherapy group did not demonstrate a superior benefit in any of the subgroups when stratified analyses were conducted based on molecular subtype, tumor size, age, and ethnicity. Chemotherapy fails to significantly improve prognostic outcomes in young patients diagnosed with early-stage breast cancer. With the help of genetic testing, these patients can expect further step-down therapy in the future.