Angiosarcoma in the breast: a population-based cohort from Sweden.

Background: Breast angiosarcoma is a rare disease mostly observed in breast cancer (BC) patients who have previously received radiotherapy (RT). Little is known about angiosarcoma aetiology, management, and outcome. The study aim was to estimate risk and to characterize breast angiosarcoma in a Swedish population-based cohort.
Methods: The Swedish Cancer Registry was searched for breast angiosarcoma between 1992 and 2018 in three Swedish healthcare regions (population 5.5 million). Information on previous BC, RT, management, and outcome were retrieved from medical records.
Results: Overall, 49 angiosarcomas located in the breast, chest wall, or axilla were identified, 8 primary and 41 secondary to BC treatment. Median age was 51 and 73 years, respectively. The minimum latency period of secondary angiosarcoma after a BC diagnosis was 4 years (range 4-21 years). The cumulative incidence of angiosarcoma after breast RT increased continuously, reaching 1.4‰ after 20 years. Among 44 women with angiosarcoma treated by surgery, 29 developed subsequent local recurrence. Median recurrence-free survival was 3.4 and 1.8 years for primary and secondary angiosarcoma, respectively. The 5-year overall survival probability for the whole cohort was 50 per cent (95 per cent c.i., 21 per cent-100 per cent) for primary breast angiosarcoma and 35 per cent (95 per cent c.i., 23 per cent-54 per cent) for secondary angiosarcoma.
Conclusion: Breast angiosarcoma is a rare disease strongly associated with a history of previous BC RT. Overall survival is poor with high rates of local recurrences and distant metastasis.
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