This case suggests that the combination of PBT and LH may be an option as a limb-preserving treatment for large inoperable MFH in the extremities.

Malignant fibrous histiocytoma (MFH) is one of the most common soft tissue sarcomas. The standard treatment is adequate surgical resection; in addition, radiation therapy plays a major role in perioperative treatment in most cases. Herein, we report the case of a patient with a large MFH who was successfully treated with combined proton beam therapy (PBT) and local hyperthermia (LH). Case presentation: A 60-year-old man presented with a 6×4-cm mass on his left thigh. Histopathology and immunohistochemistry indicated MFH, and he refused limb amputation. He received treatment with PBT at a dose at 72 GyE in 18 fractions. To cover the entire large target lesion, we used a patch-field protocol. He also concurrently received 7 courses of LH. The combination therapy achieved long-term local control without severe acute or late toxicity during the 7-year follow-up period. Conclusions: This case suggests that the combination of PBT and LH may be an option as a limb-preserving treatment for large inoperable MFH in the extremities.