(P 204) RADIATION-INDUCED ANGIOSARCOMA OF THE BREAST: RETROSPECTIVE ANALYSIS AT A REGIONAL TREATMENT CENTRE

Objective: Radiation-induced angiosarcoma (RIA) of the breast is an uncommon but morbid complication after radiotherapy for breast cancer. This retrospective study analysed the treatment and outcome of breast RIA patients at Cambridge University Hospital (CUH), a regional treatment centre in the East of England.

Methods: We retrospectively identified all patients diagnosed with and treated for breast RIA between 2010 and 2022, at CUH as well as at four other regional district hospitals who were referred to us. All patients were included in the data analysis.

Results: 22 patients were identified. The median age of RIA diagnosis was 65 years (range 41-78). The median time from completion of breast radiotherapy to RIA diagnosis was 6.5 years (range 2.4-16.0) – this interval appears to have decreased over the last 24 years (r2 = 0.6601). Tumours were often multifocal, with a median size of 65 mm (range 10-250). Two (9%) patients had metastasis at presentation. All patients underwent surgery (55% at CUH, 45% at local hospitals). Six (27%) patients received peri-operative pegylated liposomal doxorubicin (PLD) in the first-line setting.

13 (62%) patients relapsed following their primary curative-intent treatments after a median of 28 months – 10 with locoregional disease and three with distant metastases. Three patients with local recurrence received peri-operative weekly paclitaxel. After a median follow-up period of 66.5 months, the median progression-free survival (PFS) following primary curative-intent surgery was 28 months (2-year and 5-year PFS rates of 55% and 33%, respectively). The median overall survival (OS) was 82 months (2-year and 5-year OS rates of 73% and 60%, respectively). Metastases occurred in eight (36%) of our patients, the commonest sites being lung (100%) and lymph nodes (50%), followed by bone and liver.

Analysis of potential prognostic variables were performed: age (≤72 vs >72 years), tumour size ( < 5 vs ≥5 cm), surgical margin (≤1 mm vs >1 mm), hospital where the primary surgery was performed (CUH vs other hospitals), the use of peri-operative chemotherapy (vs surgery only), and peri-operative chemotherapy regimen (PLD vs paclitaxel). No factors other than age were found to be statistically significant in affecting PFS and OS. Patients of age >72 years have statistically shorter median PFS following primary surgery (6 vs 29 months; HR = 4.586 (95% CI 1.184-17.76); logrank P = 0.0275) as well as OS (45 vs 102 months; HR = 7.129 (95% CI 1.646-30.88); logrank P = 0.0086) than those who were ≤72 years.

Conclusion: RIA is an aggressive disease with high rates of recurrence, morbidity and mortality, and appears to be occurring sooner after breast radiotherapy. It is clear that more effective and personalised systemic therapies, selected or developed through in-depth understanding of the molecular and genetic basis of RIA, are desperately needed to improve the outcome of this group of patients. The current availability and provision of whole-genome sequencing for sarcoma patients in the UK could help to achieve this.