(P 510) PRIMARY BREAST ANGIOSARCOMA: CLINICAL AND PATHOLOGICAL FEATURES AND IMPACT ON OUTCOMES

Objective: Primary angiosarcoma of the breast is a rare and aggressive malignancy with a propensity for metastasis and early recurrence. There are limited data related to outcomes for this disease and the data that exist are often combined with secondary angiosarcomas of the breast. The aim of this study is to characterize a primary breast angiosarcoma patient cohort at a comprehensive cancer center and assess differences in survival based on patient and treatment factors to inform future management.

Methods: In a retrospective study, patients with a diagnosis of primary breast angiosarcoma who received care at a large tertiary cancer center from 1991 through 2021 were reviewed. Patients were excluded if they had insufficient data or short follow-up time ( < 3 months). Patients with a prior history of cancer requiring radiation to the chest were also excluded. All patients underwent surgical resection. Data were collected and analyzed using descriptive statistics and survival analysis was performed.

Results: Of 115 total patients, 97 were eligible for inclusion (Table 1). Median patient age was 40 years (range, 15 to 70 years) and 99% were female. Median tumor size was 6 cm (IQR 4, 8) and 59% were high grade. Most patients (81%) presented with a palpable breast mass with 13% presenting with skin changes such as rash, erythema, or bruising. There were 88 patients (91%) who received multimodality treatment: chemotherapy + surgery (n=32, 36%), radiation (RT) + surgery (n=14, 16%), or chemotherapy + RT + surgery (n=42, 48%). Most patients (n=66, 68%) were referred to our institution after surgery at an outside facility. The majority underwent total mastectomy (87%), with axillary assessment undertaken in 43%. Only 4 patients (4%) had metastatic disease in the nodes. Median follow-up time was 3.4 years (IQR 1.9, 6.2) with a median overall survival (OS) of 6.3 years (IQR 3, 12.5) and 5-year OS of 56%. Sixty-one percent of patients experienced recurrence with a median recurrence-free survival (RFS) of 1.8 years (IQR 1.1, 3.3). Most recurrences were distant only (n=42, 73%), commonly to bone or to multiple sites. Nine patients (16%) had local recurrence; 6 (10%) had recurrence and both local and distant sites. Patients with tumor size >5 cm had lower median OS compared to those with smaller tumors (4 vs. 11 years, p< 0.001) and those with high grade tumors had lower median OS compared to those with low (4.0 vs. 8.7 years, p=0.004) and intermediate grade tumors (4.0 vs. 6.3 years, p=0.103; Figure 1). Larger tumor size and high grade were both independently predictive of OS (Table 2), but not RFS. When stratified by decade of disease diagnosis and treatment, those treated in the earlier cohort (1991-2000) had lower median OS (Figure 2). On sub analysis of 42 patients with large tumors and high/intermediate grade, there was no difference in OS when comparing those who received trimodal treatment (n=23) to single/dual modality treatment (n=19; 3.5 vs. 4.1 years, p=0.491).

Conclusion: Most patients with primary breast angiosarcoma present at a young age with large, high grade tumors, which have poorer oncologic outcomes. Nodal positivity is rare. The majority of patients received multimodal therapy including a combination of surgical resection, chemotherapy, and radiation, however the impact of treatment modality on survival outcomes is unclear. Recurrence is common and often occurs within 2 years of diagnosis. Further research with defined treatment sequencing is needed to improve oncologic outcomes.