Supplementary Material for: Recurrent, tumor mutation burden-high, cutaneous angiosarcoma of the scalp treated with pembrolizumab.

Introduction: Chemoradiotherapy with taxanes is well-recognized as a first-line therapy for cutaneous angiosarcoma (CAS), but second-line therapy for CAS is still controversial. Case Presentation: In this report, we described a 75-year-old Japanese case of recurrent, tumor mutation burden-high CAS on the scalp treated with pembrolizumab. Our present case survived for one year despite of taxane refractory CAS with mediastinal lymph node metastasis, though the administration of anti-PD-1 Abs alone could not fully suppress the tumor progression of CAS. Conclusion: Since various factors such as pro-angiogenic molecules are corelated with the tumor progression in CAS, the administration of anti-PD-1 Abs alone could not fully suppress the tumor progression of CAS. Further novel anticancer drugs are needed in the future for the treatment of CAS.