Abstract A086: Retrospective study on postoperative adjuvant radiotherapy in primary malignant angiosarcoma of the breast patients following mastectomy or breast-conserving surgery using SEER database
Authors: Odat Ramez M. , Ibrahim Ismail A. , Ali Mohamed Ahmed , Haddadin Sara A. , Al Zoubi Bashar M. , Abohalawa Mohamed Nezar , Leeper Alexander 
Published: February 2024

Abstract
Primary Angiosarcoma of the breast (PAOB) is one of the rarest types of breast tumors, representing less than 0.2% of all breast tumors. These tumors are also associated with a poor prognosis. Mastectomy or breast-conserving surgery (BCS) are considered the best therapeutic techniques in patients with (PAOB). However, there is a debate about the need for postoperative radiotherapy (RT). PAOB is a rare tumor, therefore best management techniques are based only on expert opinion and clinical experience, which are scarce. The aim of this paper is to study the effectiveness of postoperative radiotherapy (RT) for PAOB over a long period. Patients with primary angiosarcoma of the breast (PAOB), who underwent a mastectomy and breast-conserving surgery (BCS), were identified through the Surveillance, Epidemiology, and End Results (SEER) database from 2000 to 2020. Descriptive analyses were conducted to evaluate the clinical characteristics of patients with PAOB.Age, ethnicity, year of diagnosis, grade, tumor extent, lymph node (LN) metastasis and Postoperative radiotherapy (RT) were incorporated.Cancer-specific survival (CSS) was calculated using the Kaplan Meier and compared using the log rank test. Univariate and multivariate Cox proportional hazards regressions were performed to evaluate the prognostic power of factors on (CSS). A total of 542 women with primary angiosarcoma of the breast (PAOB) were included in this study. Most women (82.8%) underwent mastectomy, while (17.2%) underwent breast conserving surgery (BCS). Postoperative radiotherapy (RT) was performed on 102 women (18.8%), with 27 (29.0%) in the BCS group and 75 (16.7%) in the mastectomy group.Postoperative radiotherapy (RT) was more likely to be performed in women with adverse risk factors, such as a larger tumor size in the mastectomy group and a higher tumor grade in both groups.Lymph node (LN) metastasis was rarely found in PAOB, only 11 patients had positive lymph node (LN) metastasis. Among those, 9 patients underwent mastectomy, and 2 patients underwent BCS. Additionally, lymph node involvement increased the chance of postoperative RT in the mastectomy group. In both groups, the need for postoperative radiotherapy (RT) increased as the tumor size became more than (3cm).However, this pattern was less obvious in the BCS group.In multivariate analysis, there weren’t any significant prognostic factors impact on Cancer-specific survival (CSS) in the mastectomy group, also, postoperative radiotherapy RT had no impact (P = 0.656).In the BCS group,age, tumor size and lymph node (LN) metastasis were significant predictive factors on Cancer-specific survival (CSS),meanwhile postoperative radiotherapy (RT) had no effect on (CSS) (P = 0.152). PAOB patients with more adverse prognostic factors received postoperative radiotherapy (RT).There was no statistically significant difference in CSS between radiotherapy (RT) group and non-(RT) group,regardless of whether the procedure is a mastectomy or a breast-conserving surgery (BCS).Further trials are needed to reach more accurate evaluations.
Citation Format: Ramez M. Odat, Ismail A. Ibrahim, Mohamed Ahmed Ali, Sara A. Haddadin, Bashar M. Al Zoubi, Mohamed Nezar Abohalawa, Alexander Leeper. Retrospective study on postoperative adjuvant radiotherapy in primary malignant angiosarcoma of the breast patients following mastectomy or breast-conserving surgery using SEER database [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A086.