(P 085) RADIATION ASSOCIATED ANGIOSARCOMAS OF THE BREAST: MULTIFOCALITY WARRANTS AGGRESSIVE ONCOLOGICAL STRATEGY

Objective: Radiation-associated angiosarcomas (RAAS) of the breast develop after a latency period within a previously irradiated field. The standard treatment for localized disease is surgery, however there is a high incidence of recurrence despite wide margin excision, and an associated poor prognosis. We evaluate the oncological outcomes of RAAS at an expert sarcoma centre receiving referrals from a major part of the country.

Methods: Cases of RAAS were identified from a prospectively maintained institutional database. RAAS were defined according to the modified criteria by Cahan et al. that included prior history of radiation therapy, a diagnosis of sarcoma distinct from the primary cancer, and location within a previously irradiated field. Clinical, pathological, and survival data for these patients was collected using the hospital electronic patient records.

Results: Between 2014 and 2021, 73 patients with RAAS of the breast were referred to our institution. The mean age was 64.5 years. Median duration from breast irradiation to development of RAAS was 6.9 years (IQR 5.3-9.9). The outcomes of patient treated with palliative intent due to advanced metastatic disease or inoperability was significantly worse than those treated with curative intent (median OS 6 months vs 70 months p < 0.001).

Multifocal RAAS had significantly worse survival compared to unifocal RAAS in patients treated with curative intent. The median OS (Figure 1) was 15 Months for multifocal RAAS while median survival was not reached for unifocal RAAS (p 0.04). Similarly, median DFS (Figure 2) was 11 months vs 36 months for multifocal and unifocal disease respectively (p 0.031). Two patients with unifocal disease managed with Wide local excision eventually required mastectomy for salvage due to recurrent disease and had no evidence of disease at last follow-up. In patients with multifocal disease who received pre-operative chemotherapy prior to surgery due to extensive local disease, a response to treatment resulted in favourable overall survival.

Conclusion: In this series, multifocal Radiation associated angiosarcoma of the breast appears biologically more aggressive with worse oncological survival compared to unifocal RAAS. This warrants an aggressive oncological strategy including the use of pre-operative chemotherapy as well as wide excision with negative margins. Response to preoperative chemotherapy showed an improved trend for overall survival.