Clinicopathologic Features And Prognostic Factors For Patients With Bone-only Metastasis Of Breast Cancer

ObjectiveBone is the most common distant metastatic site for breast cancer,among which patients with bone-only metastasis(BOM)are a special group.The purpose of this study was to compare the characteristics of clinical pathology and prognostic factors of patients with BOM and other metastatic breast cancer.MethodsRetrospective analysis was performed on the case data of patients with metastatic breast cancer admitted to Tianjin Medical University Hospital from January 2008 to December 2017,which were divided into BOM group and non-BOM group.The clinicopathological features and prognostic factors of the two groups were compared.Subgroup analysis was performed on BOM patients according to molecular subtypes,the number of bone metastasis and first-line treatment methods.Finally,the distribution of the second distant metastatic site in the patients with BOM was calculated.SPSS25.0 software was used for data processing and statistical analysis,Graph Pad Prism7 software was used to draw survival curves.Chi-square test and t-test were used for comparison between groups,Log-rank test and Cox regression model were used for univariate and multivariate analysis of prognosis,and Kaplan-Meier method was used for survival analysis.Two-tailed p-values <0.05 were considered statistically significant.Results(1)The 1290 metastatic breast cancer patients in this study were divided into BOM group(208 cases)and non-BOM group(1082 cases).The differences in hormone receptors(HR)status,human epidermal growth factor receptor 2(HER2)status,molecular subtypes and clinical stage between the two groups were statistically significant.The median overall survival(OS)of patients in BOM group and non-BOM group was 45 months and 35 months(P<0.001),respectively.(2)Univariate analysis performed on the BOM breast cancer patients showed that T stage,HR status,HER2 status,molecular types and the number of bone metastasis were all correlated with progression-free survival(PFS)(all P<0.05).HR status,molecular types,the location of bone metastasis and the number of bone metastasis were all correlated with OS(all P <0.05).Multivariate analysis showed that HR status and the number of metastasis were identified as independent influencing factors for PFS in patients with BOM(all P <0.05).HR status,the location of bone metastasis and the number of bone metastasis were identified as independent influencing factors for OS in patients with BOM(all P <0.05).(3)Univariate analysis of prognostic factors in non-BOM breast cancer patients showed that the age at diagnosis of metastasis,T stage,HR status and molecular types were all correlated with prognosis(all P<0.05).Multivariate analysis showed that the age at diagnosis of metastasis,HR status and T stage were independent factors affecting the prognosis of non-BOM patients(all P<0.05).(4)Survival analysis was performed focusing on different molecular subtypes in BOM patients and found that the PFS and OS in HR+/HER2-patients were significantly longer than HER2+ and HR-/HER2-patients(all P<0.05).Among the patients with HR+/HER2-BOM disease,the PFS and OS of patients receiving endocrine therapy or sequential therapy were significantly superior to those of chemotherapy alone(all P <0.05).(5)Survival analysis of non-BOM breast cancer patients with different molecular types showed that the PFS and OS of HR+/HER2-and HER2 positive patients were significantly longer than those of HR-/HER2-patients(all P<0.05).(6)Of the 208 BOM breast cancer patients,109(52.4%)had secondary distant metastasis.The most common secondary metastatic site was liver,followed by lung and brain.The peak period of liver or lung metastasis development was the first three years,the peak period of brain metastasis development was the first two years after the initial diagnosis of bone metastasis.Conclusion:The prognosis of BOM patients was better than that of non-BOM patients.HR negativity,axial bone metastases and multiple bone metastases were independent influencing factors for the poor prognosis of BOM patients.Age at diagnosis of metastasis≤35 years old,HR negativity and T3-4 were independent predictive factors for poor prognosis of non-BOM patients.Endocrine therapy is the preferred treatment for HR+/HER2-BOM.The most common secondary metastatic site was liver,followed by lung and brain.The liver,lung and brain should be paid close attention in 1-3 years after diagnosis of bone metastasis.