Breast conserving surgery (BCS) with adjuvant radiation therapy showed improved prognosis compared with mastectomy for early staged triple negative breast cancer patients Running title: BCS had better prognosis than mastectomy for early TNBC patients

Background: Triple-negative breast cancer (TNBC) is a subtype of breast cancer with stronger invasive capacity. For the operation strategies of early staged (stage I and stage II) TNBC patients, BCS plus radiotherapy (BCS+RT), mastectomy only (MRM only) or MRM plus radiotherapy (MRM+RT) is feasible, but no clear conclusion has been made on the choice of these treatments. Methods: The early staged TNBC patients (stage I and stage II) from the Surveillance, Epidemiology and End Results (SEER) program database between 1973 and 2014 were included in the study. Survival curves, univariate and multivariate cox proportional hazards models and propensity score weighting were applied to evaluate the prognostic impact among BCS+RT, MRM only and MRM+RT for patients. Results: Both overall and cancer-specific survival analysis showed that BCS+RT had better prognostic effect than MRM and MRM+RT in the cohort of early-staged triple-negative breast cancer patients (overall survival, P < 0.001; cancer-specific survival, P < 0.001). By taking all the risk factors into a multivariate cox proportional model, MRM and MRM+RT remained to have detrimental effect on the prognosis compared with BCS+RT as shown by either overall (HR = 1.742, CI = 1.387-2.188, P < 0.001; HR = 1.449, CI = 1.038-2.204, P = 0.029) or cancer-specific survival (HR = 1.876, CI = 1.415-2.489, P < 0.001; HR = 1.701, CI = 1.168-2.478, P = 0.006). After we performed propensity score weighting and integrated the weights for each covariate in the multivariate cox proportional model. BCS+RT remained to be prognostic beneficial compared to the other treatment options (P < 0.001). Conclusion: BCS+RT demonstrated better prognosis than MRM only and MRM+RT treatments for early-staged TNBC patients.