(P 394) DUAL OR TRIMODALITY THERAPY VERSUS SURGERY ALONE IN RADIATION-ASSOCIATED ANGIOSARCOMA OF THE BREAST

Objective: Radiation-associated angiosarcoma (RAAS) in the breast is an aggressive malignancy with high local and distant recurrence rates. There are no consensus guidelines on treatment, and institutional case series suggest either dual modality therapy (DMT; surgery + chemo) or tri-modality therapy (TMT; surgery + chemo + radiation) may improve recurrence free survival (RFS) and overall survival (OS). We sought to compare outcomes from different multidisciplinary treatment regimens to confirm findings from smaller institutional series.

Methods: Our institutional data was queried for RAAS patients presenting with localized disease and treated with curative intent. Demographic, treatment plan, recurrence, and survival data were recorded. Kaplan Meier curves for RFS and OS were plotted. Cox proportional hazards models were created to assess for variables associated with improved RFS and OS.

Results: From 2004–2023, a total of 57 patients were identified with a median follow up of 41 months. The average latency period between radiation and development of RAAS was 8.0 years, and average tumor size was 5.5 cm. Patients had either stage 2 (n=22, 39%) or stage 3 (n=33, 57%) disease and were treated with surgery alone (n=22, 39%), DMT (n=22, 39%), or TMT (n=13, 22%). Paclitaxel was the most common chemo agent used (80%) and most (63%) received this in the neoadjuvant setting. Median RFS for the surgery only group was 19.6 months vs. 39.0 months for DMT and TMT patients (P=0.1). The median OS was not met for any group by 60 months. For RFS (Table 1), Cox multivariate analysis showed age (HR 1.06, P< 0.001), size of primary tumor in cm (HR 1.10, P=0.026), and treatment group (DMT vs surgery HR=0.27, TMT vs surgery HR=0.34, P=0.021; DMT/TMT composite group vs surgery alone HR=0.30, P=0.006) to be statistically significant. Multivariate analysis for OS (Table 1) showed age (HR=1.12, P< 0.001) and treatment group (DMT/TMT composite group vs surgery HR=0.28, P=0.025) to be statistically significant, with a trend towards significance for individual treatment groups (DMT vs surgery HR=0.30, TMT vs surgery HR=0.25, P=0.078).

Conclusion: Receiving dual modality or tri-modality therapy for RAAS significantly improved RFS and OS by 70% and 72%, respectively, over surgery alone. Our findings further validate prior reports that surgical resection alone results in inferior outcomes for RAAS. The added benefit of radiation in RAS was not observed in this study but warrants further investigation with larger sample sizes.

Cox Proportional Hazards Models for (a) Recurrence Free Survival and (b) Overall Survival