Sarcoma of the breast: breast cancer history as etiologic and prognostic factor—A population-based case–control study

PURPOSE: Sarcomas of the breast account for about 1% of all breast malignancies. The aim of this national survey was to explore etiologic and prognostic factors. METHODS: Utilizing national Swedish registers, all patients registered with mesenchymal tumors in the breast during the period 1993–2013 (n = 344) were identified and compared to up to ten age and gender matched controls. Cancer history was retrieved for cases and controls. Conditional Poisson regression models were used for calculation of odds ratios. RESULTS: Previous breast cancer was overrepresented among patients with angiosarcoma. The highest risk occurred ≥ 5 years after treatment for breast cancer (OR 73.9, 95% confidence interval, CI, 25.4–215; P < 0.001). An increase in incidence of angiosarcoma was observed during the study period (1.10, 95% CI 1.05–1.16; P < 0.001). The overall incidence of breast sarcoma increased from 1.52 to 2.04 cases per million per year. Angiosarcoma of the breast was associated with a significant excess mortality compared to age-matched controls (HR 4.65, 95% CI 3.01–7.19; P < 0.001). CONCLUSIONS: Angiosarcoma increased in incidence and displayed a more severe clinical course, with significantly shorter survival. The strong association between a history of breast cancer 5 years or more prior to the diagnosis of angiosarcoma points to radiotherapy as a contributing factor. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s10549-020-05802-3) contains supplementary material, which is available to authorized users.