Abstract: Objective The aim of this study was to investigate the efficacy and prognosis of stereotactic radiotherapy(stereotactic radiotherapy,SRT)combined with lapatinib in the treatment of HER2-positive breast cancer brain metastasis. Methods A total of 91 patients with HER2-positive breast cancer brain metastases receiving lapatinib targeted therapy and whole brain radiotherapy or SRT were retrospectively analyzed.Forty-two patients received SRT and lapatinib combined with capecitabine treatment(SRT group)and another 49 patients were treated with whole brain radiotherapy and lapatinib combined with capecitabine.Curative effect and toxicity were further evaluated.Regular follow-up The related prognostic factors of patients were analyzed by multivariate Cox ragression. Results The objective response rate of brain lesions in the SRT group was 92.86%(39/42)after the end of radiotherapy;the objective response rate of the whole brain radiotherapy group was 77.55%(38/49),and the SRT group was better than the whole brain radiotherapy group(χ²=4.070,P=0.044).The Irradiated lesions progression free survival rates of 12 months in the SRT group and whole brain group were 95.20% and 83.10%,respectively.The SRT group was better than the whole brain radiotherapy group(χ²=10.851,P=0.001).There was no significant difference in the intracranial metastasis rate between the SRT group and whole brain radiotherapy group.The 1-year survival rates of the SRT group and whole brain radiotherapy group were 85.70%,69.40%,and the 2-year survival rates were 66.70% and 55.10%,respectively.The median survival time of the two groups was 31 months and 25 months,respectively.The SRT group was better than that in the whole brain radiotherapy group(P=0.002).Cox multivariate analysis showed no extracranial metastasis(HR=0.527,95% CI:0.290~0.957,P=0.035),intracranial lesions ≤3(HR= 2.457,95% CI:1.223~4.933,P=0.012),The radiotherapy SRT(HR=1.746,95% CI:1.055-2.888,P=0.030)was an independent protective factors for the prognosis of radiotherapy for brain metastases from HER2-positive breast cancer. Conclusion SRT combined with lapatinib is superior to whole brain radiotherapy combined with lapatinib in terms of local control rate and survival.Few intracranial lesions and no extracranial metastases and radiotherapy SRT is a good prognostic factor for the treatment of brain metastases from HER2-positive breast cancer.

Key words: Breast cancer, Brain metastasis, Stereotactic radiotherapy, Lapatinib