Effect Of Radiotherapy On Survival Of Stage PT_1-2N₁M₀ Breast Cancer With Different Risk Factors

Objective:To explore the effect of radiotherapy on the survival of stage p T_1-2N₁M₀breast cancer patients grouped by different risk factors,in order to provide basis for individualized radiotherapy decision-making for stage p T_1-2N₁M₀patients based on different risk factors.Methods:The retrospective analysis of data from the U.S.surveillance,epidemiology and end results program（SEER）database on 11,351 patients diagnosed between 2010 and 2017,a lot of 7928 matched patients were divided into a lot of radiotherapy group（n=3964）and a lot of no radiotherapy group（n=3964）.Single factorχ²test and t test were used to compare the differences between the groups.Multivariate Cox regression model was used to determine the independent prognostic risk factors affecting Overall survival（OS）and BCSS.Kaplan-Meier was used for subgroup survival analysis of the total population and patients stratification with different risk factors,and log-rank test was used to compare the survival differences between groups.Results:In SEER database,the median follow-up time was 80 months.The OS and BCSS of the total population of stage p T_1-2N₁M₀breast cancer were significantly benefited by post-radiotherapy of PSM,the OS was 86.6%in radiotherapy group and 82.8%in non-radiotherapy group,χ_OS²=18.250,P_OS<0.001;The BCSS in radiotherapy group（91.3%）and non-radiotherapy group（89.5%）,χ_BCSS²=7.248,P_BCSS=0.007;Multivariate analysis after PSM showed that marital status,age,race,Grade,radiotherapy,proportion of axillary lymph node metastasis,molecular typing,and tumor size were independent prognostic factors for BCSS,with age>62 years（HR=1.484,95%CI:0.633～0.846,P<0.001）,Grade III（HR=1.973,95%CI:1.673-2.326,P<0.001）,axillary lymph node metastasis ratio>7%（HR=1.357,95%CI:1.081～1.704,P=0.009）,triple negative type（HR=2.102,95%CI:1.746-2.530,P<0.001）,tumor size 2.4cm-5cm（HR=1.778,95%CI:1.525-2.074,P<0.001）were independent prognostic risk factors for BCSS;In subgroup analysis,radiotherapy improved BCSS in high-risk group（89.5%）and non-radiotherapy group（86.7%）,χ_BCSS²=11.049,P_BCSS=0.001;In the medium risk group,the radiotherapy group（96.4%）and the non-radiotherapy group（96.0%）,χ_BCSS²=0.090,P_BCSS=0.764,there was no significant difference between the two groups.In the low-risk group,the radiotherapy group（94.6%）and the non-radiotherapy group（98.8%）,χ_BCSS²=4.678,P_BCSS=0.031,radiotherapy increased the specific mortality of patients.Multivariate logistic regression analysis showed that radiotherapy could reduce the risk of LRR by 78.7%（OR=0.213,OR 95%CI:0.102-0.325,P<0.001）.The proportion of axillary lymph node metastasis was>7%（OR=3.783,OR 95%CI:2.976-5.382,P=0.003）and Ki-67 value was≥30%（OR=5.348,OR 95%CI:1.312～21.803,P=0.019）and vascular invasion（OR=4.899,OR 95%CI:1.587～15.119,P<0.001）were independent risk factors for LRR.Kaplan-Meier analysis showed that the LRC at 5 years after modified radical surgery in the radiotherapy group was 89.4%vs.56.5%（χ²=27.476,P<0.001）.Conclusion:Radiotherapy can significantly reduce the risk of local recurrence in patients with stage p T_1-2N₁M₀breast cancer,but the benefits of radiotherapy in patients with different risk factor groups are significantly different,so the radiotherapy for this group should be individualized.Radiotherapy should be considered in high-risk patients,cautiously recommended in moderate-risk patients,and not used in low-risk patients.