Primary Angiosarcoma of Breast: Surgery Alone Versus Chemotherapy and/or Radiotherapy—A Systematic Review and Meta-Analysis

Background: Primary angiosarcoma of the breast (PAB) is a rare malignancy with no standardized treatment protocol. Objective: To quantify the impact of tumor grade on overall survival (OS) and evaluate the association of adjuvant chemotherapy and radiotherapy with survival in primary angiosarcoma of the breast (PAB). Methods: We systematically searched PubMed, Scopus, and Cochrane Library until 27 June 2025. Two reviewers independently screened studies, extracted data, and assessed risk of bias using the Newcastle-Ottawa Scale. Kaplan–Meier curve digitization was used to reconstruct individual patient data. Random-effects meta-analysis was performed for grade comparisons and therapy associations. Results: Eleven studies (436 patients) were included. Meta-analysis of six studies showed increasing tumor grade significantly predicted mortality, with homogeneous hazard ratios (HRs) of 1.2 (Grade 2 vs. 1) and 3.7 (Grade 3 vs. 1). Analysis of five studies revealed that adjuvant chemotherapy was associated with significantly improved survival (HR = 0.11, 95% CI: 0.02–0.45), while radiotherapy showed no benefit (p = 0.96). Included studies demonstrated low-moderate risk of bias. Conclusions: This first quantitative synthesis establishes histologic grade as a paramount prognostic factor in PAB and shows a strong association between adjuvant chemotherapy and survival benefit. These findings provide crucial evidence for risk stratification and support considering chemotherapy in multimodal treatment for this rare disease.