The Role Of Radiotherapy For The Postoperative HER2-positive Early Breast Cancer

Objective: To evaluate the effect of postoperative radiotherapy on the prognosis of early HER2-positive breast cancer patientsMethods: Retrospective study included HER2-positive breast cancer patients from 1st Jan.2015 to 31 st Dec.2018 in the First Affiliated Hospital of China Medical University,and collected general patients’ information such as name,age,primary site,clinical and pathology diagnosis,lesion diameters,histology,stage,number of lymph nodes metastasized,ER,PR,HER-2,Ki-67,surgery approach and postoperative adjuvant treatments,etc.Kaplan-Meier was utilized to obtain 3-year OS,DFS,LRRFS and DDFS,with Log-rank test comparing the difference;Cox regression model was adopted for univariate and multivariate analysis;Nomography was used to establish prognosis model for all irradiated patients,C-Index and calibration curve checked discrimination and heterogeneity.P<0.05 represents statistical significance.Results: A total of 321 patients with stage 0-II HER2-positive breast cancer were followed up in this study,of which 118 patients received radiotherapy.According to whether or not to receive radiotherapy,the 3-years OS of the whole group was(82.4% vs 88.5%,p=0.36),3-years DFS(81.2% vs 88.5%,p=0.12),3-years LRRFS(78.3% vs 87.4%,p=0.13),3-years DDFS(81.6% vs 87.8%,p=0.3).After PSM,both the radiotherapy group and the non-radiotherapy group were 98 patients.There were no significant difference among 3-years OS,DFS,LRRFS and DDFS.Subgroup analysis of patients who received targeted therapy after radical surgery in groups of ≥55 years old vs <55 years old,T0-1 vs T2-3,p N0 vs p N1,none of them was observed significant benefits from radiotherapy.Cox proportion regression model multivariate analysis suggests the expression of Ki-67 is an independent factor affecting DFS(HR 1.51,95%CI 1.04-2.19,p=0.03)and LRRFS(p=0.025).Among 91 patients with HER2 positive DCIS,52 patients did not receive chemotherapy or targeted therapy after surgery.Compared with the same group of patients who received chemotherapy,radiotherapy or targeted therapy,there was no significant difference in prognosis.Nomogram established a prognostic model of 118 patients receiving radiotherapy,those whose aged less than 55,pathological of DCIS with infiltrating component or invasive breast cancer,tumor size larger than 2cm(T2-3),ER and PR slightly or moderately positive could benefit more from postoperative adjuvant radiotherapy.Conclusion: For patients with HER2-positive p T0-2N0-1M0 stage,the absolute benefit of adjuvant radiotherapy after radical resection is not obvious,especially after receiving trastuzumab,radiotherapy cannot further improve OS,DFS,LRRFS and DDFS.The level of Ki-67 is an independent factor affecting DFS.For postoperative DCIS patients younger than 55 years old with low Ki-67 expression,there is no significantly absolute benefit from chemotherapy,radiotherapy,and targeted therapy.