Comparison Of Prognosis Between Young And Old Patients With Operable Breast Cancer Based On Propensity Score Matching

Objective:To compare the clinicopathological features and treatment options of young and old patients with operable breast cancer,and to explore the influence of age on the prognosis of breast cancer.Methods:Female patients with primary unilateral invasive breast cancer who underwent breast surgery at the First Hospital of Jilin University between September 2005 and October 2017 were included.According to the entry criteria,patients≤40 years（n=395）were included in the young group and patients≥60 years（n=761）were included in the old group.Follow-up was performed via telephone or outpatient service.The survival time of each patient was defined as the difference in time between the date of initial diagnosis until the date of recurrence,metastasis,death,or the end of the last follow-up.Statistical analysis was performed using SPSS statistics software version26（IBM Corp.,Armonk,NY,USA）.Quantitative data that did not conform to the normal distribution are described as median and interquartile range.Qualitative data were compared using the chi-square test or two independent non-parametric sample tests（Mann-Whitney U test）,and the level of significance was set at P<0.05.The survival curve was drawn using the Kaplan-Meier method and compared with the log-rank test,with the level of significance set at P<0.05.Univariate and multivariate analyses were performed using COX models,and the level of significance was also set at P<0.05.The Propensity Score Matching Method（PSM）was used to match and balance the influence of confounding factors and to eliminate the selective bias at a ratio of 1:1.The DFS and OS of the two groups were compared before and after matching respectively.Results:The young group had a higher proportion of c T₃（4.6%vs.1.8%,P=0.008）and Luminal B than the old group（51.9%vs.41.9%,P<0.001）and axillary lymph node involvement（42.8%vs.35.6%,P=0.017）was more common than old group at the time of admission.Statistical differences in all data regarding treatment options,except for axillary lymph node surgery and adjuvant endocrine therapy,were observed between the two groups.Young patients were more likely to choose breast-conserving or reconstructive surgery（25.1%vs.15.6%,P<0.001）and received neoadjuvant chemotherapy（19.2%vs.12.9%,P=0.004）,adjuvant chemotherapy（79%vs.51%,P<0.001）,radiotherapy（44.6%vs.26.4%,P<0.001）,targeted therapy（25.6%vs.14.5%,P<0.001）than the old patients.364 pairs of patients were included after adjusting by PSM.Survival analysis showed that DFS,but not OS,was statistically significant between the two groups（DFS:P=0.001,hazard ratio=0.538,95%confidence interval=0.371–0.781;OS:P=0.549）.Further subgroup analysis found that age was an independent risk factor for DFS only in Luminal B type subgroup（P=0.038,HR=0.470,95%confidence interval 0.231-0.958）.Conclusion:Young age（≤40 years old）was an independent risk factor for DFS in breast cancer after multivariate and PSM analyses were performed to balance confounders.The young group had a higher proportion of c T₃,Luminal B and axillary lymph node involvement than old group at the time of admission.