Boron neutron capture therapy for cutaneous angiosarcoma and malignant melanoma: First in-human phase I clinical trial.

Background and purpose: Definitive radiotherapy for patients with scalp angiosarcoma has a poor prognosis, often resulting in severe skin adverse events. Additionally, malignant melanoma is known for its radioresistant nature. Boron neutron capture therapy (BNCT) may address these challenges due to the high uptake capacity of boron drugs in these cancer types. We aimed to determine the treatment dose for BNCT and evaluate the incidence of acute adverse events AEs following BNCT in patients with primary or recurrent angiosarcoma/malignant melanoma of the skin.

Materials and methods: This was a single-center, non-randomized clinical trial with a three-step dose escalation plan, involving maximum skin doses of 12, 15, and 18 Gy-Eq following a 3 + 3 design. The patients underwent BNCT between November 2019 and April 2022. The primary endpoint was to evaluate the incidence of acute adverse events.

Results: Ten patients (scalp angiosarcomanine, forefinger malignant melanoma: one) were included. The median target lesion size was 46.5 (range: 20-145) mm. A transient asymptomatic increase in serum amylase level was the only grade 3 adverse event. The best overall response rate within 180 days was 70 % (median tumor shrinkage rate: 77.5 % [4.9-100 %]).

Conclusions: BNCT with a dose of 18 Gy-Eq is a feasible treatment option, demonstrating a favorable safety profile and a high response rate in patients with primary or recurrent angiosarcoma or malignant melanoma of the skin.