Effectiveness of chemotherapy on prognosis of elderly breast cancer: A retrospective cohort study based on SEER database.

Abstract

e12525 Background: The estimated population of breast cancer older than 70 years is over 80,000 new onset cases in 2019 and keep increasing. Currently, the proportion of standard chemotherapy for elderly patients was much lower than that for young patients, due to shorter life expectancy, more comorbidities, and concerns over increased toxicities and reduced tolerance. Till now, few evidences from clinical trials could support the use of chemotherapy for elderly patients, as also indicated by current guidelines for adjuvant chemotherapy. The effectiveness of chemotherapy for elderly breast cancer remains to be further verified. Methods: We identified 75,525 female breast cancer patients aged 70 years and older in the Surveillance, Epidemiology, and End Results (SEER) database from January 1, 2010, to December 31, 2016, and excluded those patients with secondary, metastatic, or bilateral breast cancer, not confirmed by pathology, lacking of key information, dead or loss to follow-up in 6 months after diagnosis. Propensity score matching (PSM) (PSM ratio: 1:1, caliper: 0.2* standard deviation of propensity score) was applied to construct balanced cohorts with or without chemotherapy based on demographic and pathophysiological characteristics. Kaplan-Meier analysis, multivariable Cox proportional model, and subgroup analysis were performed to evaluate the effectiveness of chemotherapy on overall survival (OS) and breast cancer-specific survival (BCSS). Results: A total of 33,177 eligible patients were included, of them, 5273 (15.89%) received chemotherapy. Through PSM, 8360 patients were successfully matched and almost reached balances between groups. In matched dataset, patients receiving chemotherapy exhibited a better prognosis on OS and BCSS (the 5-year survival rate, OS: 0.80 [0.78-0.82] with chemotherapy vs. 0.71[0.69-0.73] control; BCSS: 0.88 [0.87-0.89] with chemotherapy vs. 0.85 [0.84-0.86]; both log-rank test, P < 0.001); in multivariable Cox analysis, chemotherapy was associated with a 35% and 21% risk reduction on OS (HR [95%CI]: 0.65[0.59-0.72]) and BCSS (0.79[0.69-0.91]), respectively. Furthermore, subgroups with HER-2 positive, or more lymph nodes involved, were inclined to benefit more from chemotherapy. Conclusions: Our study provided additional evidences that chemotherapy may improve the prognosis of elderly breast cancer, especially for those subpopulations benefit more from chemotherapy treatment.