Abstract P2-14-10: Metastatic pattern discriminates survival benefit of primary surgery for de novo stage IV breast cancer patients: A longitudinal cohort study
Authors: Wang K , Shi Y , Zhang X , Ren G-S , Li H-Y 
Published: May 2019

Abstract
Background: Primary tumor resection for patients(pts) with de novo stage IV breast cancer(BC) was controversial among recent clinical trials. Indeed, considerable discrepancy in metastatic pattern between those studies was considered as a potential reason for their inconsistent results. We sought to determine the survival benefit of primary surgery on the basis of metastatic pattern.
Methods: A retrospective cohort study based on the SEER database was conducted to identify pts with de novo stage IV BC diagnosed between 2010 and 2015. Pts were divided into a surgery and a non-surgery group, and propensity score weighting was used to balance clinicopathologic factors between groups.
Results: Of 8,142 de novo stage IV BC pts with a total of 12,737 sites of distant metastases identified in this study, 1,891(23%) cases were managed with surgery and 6,251(77%) cases were managed without surgery. There were 3,821 all-cause deaths and 3,291 BC specific deaths over a median follow-up of 22 months. The weighted 3-year overall survival(OS) for the surgery group was 54.5%, compared to 47.7%(HR=0.82;0.78 to 0.86,P&lt;0.001) for the non-surgery group. The magnitude of the survival difference with surgery was significantly correlated with metastatic patterns(Pinteraction&lt;0.05). Significant survival improvements in surgery group compared with non-surgery group were observed in pts with bone-only metastasis(adjusted HRos=0.83;0.76 to 0.90,P&lt;0.001) or multiple metastases with bone involved (adjusted HRos=0.76;0.70 to 0.83,P&lt;0.001), whereas survival inferiority of surgery was found for pts with multiple visceral organs-only metastases(adjusted HRos=2.08;1.39 to 3.11,P&lt;0.001).
Hazard ratios comparing survival between surgery group and non-surgery group according to metastatic patterns.Metastatic patternNo. of Patients (Non-surgery group/Surgery group)Weighed* 3-year OS (%) (Non-surgery group/Surgery group)Weighed Multivariable*† HR of OSPWeighed* 3-year BCSS (%) (Non-surgery group/Surgery group)Weighed Multivariable*† HR of BCSSPDistant Lymph nodes-only285/19255/550.960.7164/581.160.2Bone-only2409/70454/640.83&lt;0.00157/670.8&lt;0.001Brain-only34/1615/90.420.0119/150.520.08Lung-only434/27046/520.90.1950/600.750.001Liver-only378/20353/511.160.1458/551.130.23Bone ± non-visceral ± visceral organs2305/38841/500.76&lt;0.00145/530.74&lt;0.001Non-visceral ± visceral organs302/8943/500.780.0646/530.750.03Visceral organs-only104/2931/222.08&lt;0.00136/281.290.25(*)Weighted by inverse propensity score.(†)Aadjusted for age,year of diagnosis,race,marital status,grade,histologic type,tumor size,ER,PR,HER2 status,chemotherapy. BCSS, breast cancer specific survival.
Conclusion: The survival benefit offered by surgery for de novo stage IV BC varies by metastatic patterns. Local surgery for pts with bone-only metastasis or high metastatic burden accompanied by bone metastasis offers a significant survival advantage over non-operative management, whereas the opposite effect is observed among simultaneous liver and lung metastasis pts. Decisions for primary surgery of de novo stage IV BC pts should be tailored according to metastatic pattern, and mechanisms of bone/visceral organs-only/first metastasis BC are needed further understanding.
Citation Format: Wang K, Shi Y, Zhang X, Ren G-S, Li H-Y. Metastatic pattern discriminates survival benefit of primary surgery for de novo stage IV breast cancer patients: A longitudinal cohort study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-14-10.