Comparison Of Prognostic Differences Between Breast-conserving Surgery And Total Mastectomy For Early Breast Cancer Based On A Propensity Score Matching Method

Objective:Comparison of prognostic differences between breast-conserving surgery and total mastectomy for early breast cancer based on a propensity score matching method.Methods:A total of 1879 female breast cancer patients with primary invasive,pathological stages of T1-2,N0-1 and M0 in the Department of Breast Surgery,First Hospital of Jilin University were selected from September 2005 to December2016.Among them,379 patients received BCS and 1500 patients received TM.Clinical data（including age,menstrual status and treatment modality）and pathological data（including tumour histological type,tumour stage,T-stage,N-stage and molecular typing）were collected to compare the differences in clinicopathological characteristics between the two groups,and Kaplan-Meier survival curves and Log-Rank tests were applied The differences in the distribution of DFS and OS survival curves between the groups were compared,and Cox proportional risk regression models were applied for univariate and multivariate analyses to discuss the effect of surgical approach on DFS and OS in breast cancer patients.The propensity score matching（PSM）method was then used to match patients receiving BCS and TM in a 1:1 ratio using the caliper matching method,with the caliper Chi set at 0.0005.367 patients each receiving BCS and TM were obtained after matching.The differences in clinicopathological characteristics between the two groups were not statistically significant.Kaplan-Meier survival curves and Log-Rank tests were applied to compare the DFS and OS of the two groups after matching to analyse the impact of surgical treatment on patient prognosis under conditions where other clinicopathological factors were consistent.Results:（1）The differences in several clinicopathological characteristics between the BCS and TM groups were statistically significant.Among them,younger patients（<40years old）were more likely to opt for breast-conserving surgery（17.1% vs 10.9%,P=0.003）and a higher proportion of postmenopausal（56.2% vs 47.6%,P=0.003）patients in the BCS group,with invasive ductal carcinoma predominating in both groups.In terms of tumour stage,the BCS group had a higher and statistically significant proportion of patients with T1（74.7% vs 58.9%,P<0.001）and N0（79.9vs 72.9,P=0.005）.26.3%),which was statistically significant（P < 0.001）.In terms of postoperative treatment options,more patients in the BCS group received adjuvant endocrine therapy（73.6% vs.67.5%,P=0.022）,which was statistically different.However,there was no statistical difference between the two groups in terms of postoperative adjuvant chemotherapy（P=0.063）.（2）Before PSM,with a median follow-up of 87 months（1-192）,27 cases（7.1%）of recurrent metastases and 18 deaths（4.7%）occurred in the BCS group;154 cases（10.3%）of recurrent metastases and 112 deaths（7.5%）occurred in the TM group.The results of survival analysis showed that the 5-year OS of the BCS and TM groups were 96.4% and 95.6%,respectively,which were statistically different（P=0.016）,and the DFS of the two groups were 95.9% and 93.1%,respectively（P=0.026）,which were statistically different.（3）Recurrent metastases occurred in 21 cases（5.7%）and 13 deaths（3.3%）in the BCS group after PSM matching;metastases occurred in 94 cases（25.6%）and 63patients（17.2%）died in the TM group.Survival analysis showed that the 5-year OS was 96.5% and 89.5% in the BCS and TM groups respectively,which was statistically different（p<0.001）.The DFS of the two groups was 96.0% and 81.5%,respectively,with a statistical difference of P < 0.001.（4）Subgroup analysis of patients according to different molecular subtypes and survival analysis showed that in the luminal B subgroup both OS（p=0.002）and DFS（p=0.007）were better in the BCS group than in the TM group and were statistically different.Conclusion:The PSM method confirmed that patients in the BCS+RT group had better OS and DFS than those in the TM group.Patients in the luminal B subgroup who underwent breast-conserving surgery had better outcomes.