We assessed the impact of participating to clinical research among 1727 women with localized breast cancer. Using as referent individuals not treated according to guidelines for systemic therapy, the adjusted hazard ratio of death was 0.70 (95% confidence interval (CI): 0.54,0.90, p-value: 0.006) in those treated according to current guidelines and 0.45 (95% CI: 0.27,0.73, p-value: 0.001) in participants to research. Participation to clinical trials results in a substantial gain in survival.