Effect Of Postmastectomy Radiotherapy On Locoregional Control And Disease-free Survival In Patients With Breast Cancer Treated With Neoadjuvant Chemotherapy

Purpose: To explore the effects of postmastectomy radiotherapy(PMRT)on patients receiving neoadjuvant chemotherapy(NAC)for locoregional recurrence rate(LRR)and disease-free survival(DFS).Methods: We retrospectively analyzed the clinical data of 544 patients with clinical stage II-III breast cancer who underwent NAC and modified radical mastectomy treated in our center from 2007 to 2015,including neoadjuvant chemotherapy regimens,neoadjuvant chemotherapy cycles,tumor size,clinical TNM staging,histopathological classification,pathological TNM staging,targeted therapy,endocrine therapy,PMRT,etc.Using chi-square test or Fisher’s exact probability method to compare the difference in baseline data between the radiotherapy group and the non-radiotherapy group.The Kaplan-Meier method was used to draw the survival curves of the two groups of patients(including LRR and DFS),and the Log-rank test was used to compare the survival differences between the two groups.Cox regression analysis was used to determine the independent prognostic factors of LRR and DFS.According to clinical stage,postoperative T stage and postoperative N stage,patients can be further divided into different subgroups.In different subgroups,Kaplan-Meier method and Log-rank test was used to compare the radiotherapy group and the non-radiotherapy group in LRR and DFS The difference.Results:(1)A total of 544 patients were enrolled in this study,There were 394(71.1%)and 160(28.9%)patients with cⅡ and cⅢ,respectively.The median follow-up time of the entire cohort was 65 months(12-153 months).A total of 399(72.0%)patients received PMRT and 155(28.0%)did not.Amongst the patients,58(10.5%)had locoregional recurrence,138(24.9%)had distant metastasis and 72(13.0%)patients died.(2)There were significant differences in tumor size,clinical N staging,clinical TNM staging,p CR,pathological T staging,and pathological N staging between the radiotherapy group and the non-radiotherapy group,but there were no differences in age,menstrual status,histological grade,pathological type,ER status,PR status,HER-2status.(3)The 5-year LRR and DFS of the radiotherapy group and non-radiotherapy group were 9.2% and 74.2%,respectively.There was no significant difference in 5-year DFS between the two groups(74.0% vs.74.8%,p=0.99),but the 5-year LRR of the radiotherapy group was significantly lower than that of the non-radiotherapy group(7.3% vs.14.1%,p=0.01).(4)Multivariate analysis found that PR-,yp N2-3 and without PMRT were the independent risk factors of LRR;PR-,TNBC,yp N1,yp N2-3 and without PMRT were the independent risk factors of DFS.(5)According to the subgroup analysis based on the clinical stage,among patients with stage c II,there was no significant difference in DFS between the radiotherapy group and the non-radiotherapy group(p=0.648),but the LRR of the radiotherapy group was significantly lower(p=0.001);Among patients with stage cⅢ,there was no significant difference between the two groups in LRR and DFS,but the radiotherapy group had a certain trend of benefit in DFS.(6)According to the subgroup analysis based on the pathological T stage,there was no significant difference in LRR and DFS between the radiotherapy group and the non-radiotherapy group in T0/Tis patients;In T1 and T2-4 patients,the LRR of the radiotherapy group was significantly reduced.There was no significant difference in DFS in the two groups between the radiotherapy group and the non-radiotherapy group,but the radiotherapy group had a certain trend of benefit in DFS.(7)According to the subgroup analysis based on the pathological N stage,there was no significant difference in LRR and DFS between the radiotherapy group and the non-radiotherapy group in yp N0 patients;In yp N1 and yp N2-3 patients,the LRR and DFS of the radiotherapy group were better than those of the non-radiotherapy group.Conclusion: PMRT could significantly reduce the LRR of breast cancer patients with stage Ⅱ-Ⅲ neoadjuvant chemotherapy.PMRT was an independent prognostic factor of LRR and DFS.In cⅡ,pathological T1,T2-4 patients,the LRR of the radiotherapy group was significantly reduced;In patients with stage cⅢ and T2-4,the radiotherapy group had a certain trend of benefit in DFS;in patients with stage yp N1 and yp N2-3,the LRR and DFS of the radiotherapy group were better than those of the non-radiotherapy group.