(P 063) A RETROSPECTIVE COHORT ANALYSIS EVALUATING THE NATURAL HISTORY AND CHARACTERISTICS OF ANGIOSARCOMAS OF THE BREAST

Objective: Angiosarcoma is a rare complication of breast conserving therapy for breast cancer, with an incidence of 1/1000 patients at ten years after completion of local breast cancer treatment. While most cases are caused by radiation or chronic lymphedema (Stewart-Treves Syndrome), breast angiosarcomas can also occur de novo in patients without a history of breast neoplasm. Secondary and primary breast angiosarcomas have been recently recognized as harboring different molecular alterations. Due to the rarity of this disease and lack of standardized management approaches, there are limited data regarding long-term outcomes that can appropriately benchmark endpoints for future interventional trials. The primary aim of the study was to evaluate characteristics and survival outcomes of patients with breast angiosarcomas.

Methods: Breast cancer and angiosarcoma cases were abstracted from the Surveillance, Epidemiology, and End Result (SEER) database (data source: SEER 18 Regs Custom Data (with additional treatment fields), Nov 2018 Sub (1975-2016 varying) - Linked To County Attributes - Total U.S., 1969-2017 Counties). Secondary breast angiosarcomas (SBA) were defined as angiosarcomas located in the breast occurring after a prior breast cancer diagnosis in the same individual (identical SEER patient ID). Primary breast angiosarcomas (PBA) were defined as cases with an angiosarcoma diagnosis listed as “one primary only”. Patients with incomplete survival follow up, distant or missing SEER stage, and PBA cases diagnosed prior to year 1992 were excluded. Survival was analyzed by the Kaplan-Meier method and compared using log-rank tests, Cox proportional hazard models were used to assess the association of clinicopathological characteristics on overall survival (OS).

Results: The study population consisted of 193 patients with locoregional SBA and 145 patients with locoregional PBA. In patients with SBA, the median interval between breast cancer and angiosarcoma diagnoses was 8 years (IQR: 6,10). All patients were female (see Table 1). The median age at diagnosis for SBA and PBA was 75 (IQR: 64,82) and 50 (IQR: 34, 69), respectively. The majority of both SBA and PBA populations received surgery for their angiosarcoma (95% and 98% respectively). In the SBA group, 9% received radiation and 23% received chemotherapy for treatment of locoregional angiosarcoma while 51% received radiation and 31% chemotherapy for treatment in the PBA group. Clinical characteristics of the patients at time of angiosarcoma diagnosis are reported in Table 1. The median OS for SBA is 43 months (95% CI: 32-66 months) and 69 months (95% CI: 41 months- not reached) for PBA. The SBA 1-, 5-, and 10-year OS are 82% (95% CI: 75%-86%), 45% (95% CI: 37%-53%), and 28% (95% CI: 20%-37%). The PBS 1-,5-, and 10-year OS are: 89% (95% CI: 83%-93%), 52% (95% CI: 43%-55%), and 47% (95% CI: 37%-55%). For SBA, increasing age, tumor size, tumor grade, SEER stage, and absence of surgery were associated with OS on univariable analysis. For PBA, increasing tumor size, tumor grade, lymph node involvement, and SEER stage were associated with OS (Table 2).

Conclusion: For patients with breast angiosarcoma, overall survival is better for patients with primary disease, while surgery remains the mainstay of locoregional treatment, better systemic therapies are needed to improve long-term outcomes. Data from this study may be utilized to benchmark the endpoint of OS for future interventional clinical trials.

Table 1 CTOS 2022.docx

Table 2 CTOS 2022.docx