Difference Analysis Of Metastasis Patterns And Prognosis Of Newly Diagnosed Stage Ⅳ Breast Cancer With Different Primary Tumor Sizes And The Value Of Primary Tumor Surgery

Objective: Analyze the relationship between tumor size and metastatic behavior,prognosis,as well as the application value of primary tumor surgery,in order to bring more ideas for the precise treatment of newly-treated stage Ⅳ breast cancer.Methods: The SEER database was used to screen women with stage Ⅳ breast cancer diagnosised at 2010-2015.Chi-square test was used to analyze the relationship between tumor size and the location of metastasis;Log-rank test and Cox regression were used to analyze the tumor size and the effect of primary tumor surgery on the prognosis;Logistic regression analysis was used to analyze the influencing factors of primary site surgery.Results: 1.The relationship between tumor size and the sites of metastasis: HR+/HER2-subtype: The proportion of bone metastasis(42.5%)of the tumor size>5cm(group S3)was lower than that of tumor size≤2cm(group S1)(52.1%)and 2~5cm(S2 group)(51.1%),and the proportion of multiple sites(33.4%)and lung metastasis(9.0%)were higher than that of S1 group(24.9%,5.7%)and S2 group(27.0%,6.9%)(P<0.001).HR+/HER2+ subtype: Regardless of bone(28.8% VS 34.9%),brain(1.1% VS 1.4%),liver(16.2% VS 12.2%),lung(9.2% VS 9.8%),multi-site metastasis(36.9% VS 32.1%),there were no significant differences between the S1 group and the S2 group(P=0.209);there was difference only in the incidence of liver metastasis(8.0% VS 16.2%)compared with the S3 group and S1 group(P=0.004);compared the S2 group,the proportion of liver metastasis(8.0% VS 12.2%)and bone metastasis(27.3% VS 34.9%)were lower,and the proportion of multi-site metastasis(41.4% VS 32.1%)was higher in the group S3(P<0.001).HR-/HER2-subtype: There were no statistical differences in the proportion of brain,liver,and multi-site metastasis among the three groups(all P>0.05);The proportion of bone metastasis in the group S3 was lower than that of the group S1(17.6% VS 27.0%)(P<0.001);the incidence of lung metastasis increased with the increasing of tumor size(group S1: 10.1%;group S2: 18.3%;group S3: 24.9%)(P<0.001).HR-/HER2+ subtype: Regardless of the sites of metastasis,there were no statistical differences between the three groups(group S1 VS group S2: P=0.968;group S1 VS group S3: P=0.368;group S2 VS group S3: P=0.065).2.The relationship between tumor size and the prognosis: The risk of death of patients with a tumor size 2~5cm was 1.092 times compared with patients with a tumor size≤2cm(HR=1.092,P=0.021);the risk of death of patients with a tumor size>5cm was 1.27 times than patients with tumor size≤2cm(HR=1.270,P<0.001).Based on subtypes stratification,HR+/HER2-subtype: The three groups of MST were 39 months VS 38 months VS 31 months(P<0.001);there was no significant difference between the S2 group and the S1 group(P=0.432);HR+/HER2+ subtype: The three groups of MST were 55 months VS 50 months VS 43 months(P=0.005);there was no significant difference between the S1 group and the S2 group(P=0.879);HR-/HER2-subtype: The three groups of MST were 14 months VS 14 months VS 12 months(P=0.091);HR-/HER2+ subtype: The three groups of MST were 41 months VS 45 months VS 34 months,only the group S2 was statistically different from the group S3(P=0.043).3.Surgery significantly reduced the risk of death(HR=0.593,P<0.001).Based on the stratification of the tumor size,the MST of the surgical group was significantly longer than that of the non-surgical group(S1 group: 63 months VS 29 months;S2 group: 49 months VS 28 months;S3 group: 34 months VS 24 month),surgery significantly reduced the risk of death(S1 group: HR=0.484,P<0.001;S2 group: HR=0.549,P<0.001;S3 group:HR=0.679,P<0.001).Conclusions: 1.HR+/HER2 subtype: Tumor size>5cm had a higher proportion of lung and multi-site metastasis and a lower proportion of bone metastases than tumor size≤2cm,2~5cm;HR+/HER2+ subtype: There was no significant difference in the proportion of distant metastases between tumor size≤2cm and 2~5cm,the proportion of liver metastasis in tumor size>5cm was lower than that of tumor size≤2cm and 2~5cm;HR-/HER2-subtype: The proportion of lung metastasis increased with the increasing of the tumor size;HR-/HER2+ subtype: Regardless of the metastasis sites,there were no statistical differences in the incidence of the three groups.2.Tumor size>5cm was a risk factor for poor prognosis in patients with HR+/HER2-,HR+/HER2+,HR-/HER2+ subtypes;in HR-/HER2-subtype,different tumor sizes had no significant effect on the prognosis difference.3.Primary tumor surgery was an independent favorable prognostic factor,the smaller of the primary tumor,the more obvious the improvement of the prognosis by surgery.