Definitive Radiotherapy Using Electron Beam and Intensity-modulated Radiotherapy for Unresectable Angiosarcoma of the Scalp

Background/Aim: Radiotherapy for angiosarcoma of the scalp has not been standardised yet. Hence, we aimed to retrospectively analyse the outcomes of patients treated with electron beam therapy or intensity-modulated radiation therapy (IMRT) for unresectable angiosarcoma of the scalp. Patients and Methods: Data from patients treated with chemoradiotherapy or radiotherapy alone for unresectable angiosarcoma of the scalp between March 2009 and March 2021 were evaluated. Survival and local control rates were analysed using the Kaplan-Meier method, and the log-rank test was used to compare groups. Adverse events were analysed using the Common Terminology Criteria for Adverse Events ver. 5.0. Results: Sixteen patients were eligible for the study. Eight patients were treated with electron beam therapy and eight patients with IMRT. The median follow-up period was 18.0 months. The median radiation dose was 57 Gy in 19 fractions in the electron beam therapy group and 70 Gy in 35 fractions in the IMRT group. In the IMRT group, acute non-haematologic toxicity was observed in two patients with grade 3 dermatitis. The one-year overall survival rate, progression-free survival rate, and local control rate in the electron beam therapy group were 80.8%, 56.3%, and 77.4%, respectively, and the corresponding values in the IMRT group were 100%, 75%, and 100%, respectively. One-year local control was significantly better in the IMRT group compared to that in the electron beam therapy group (p=0.016). Conclusion: IMRT for angiosarcoma of the scalp may improve local control rates compared to electron beam therapy, but long-term follow-up studies are required to validate this finding.