[Intraoperative radiotherapy in malignant bone tumors]

When a bone tumor is confirmed to be malignant by biopsy and has not expanded into the soft tissue, intraoperative radiation therapy (IORT) is indicated for most parts of the four extremities. The irradiation area is exposed through an extensive skin incision, and the soft tissues are opened and retracted away from the irradiation area, leaving a layer of normal tissue directly covering the tumor. The irradiation is performed with 12-26 MeV electron beams from a betatron at a dose of 50-100 Gy, depending on the radiosensitivity of each tumor. The multifocal bilateral irradiation method is the best for minimizing complications of the soft tissues. Since 1978, we have performed IORT in combination with chemotherapy in 41 cases of malignant bone tumors and experienced only five cases of tumor recurrence one in the irradiated area and four in the non-irradiated area. Joint function in the irradiated limb was excellent. However, due to the high incidence of pathological fracture after IORT in osteolytic tumors, the limb eventually had to be replaced by a prosthesis. After 1984 when cisplatinum was introduced to our chemotherapy protocol, the cumulative 5 year survival rate increased to 81%, with the irradiated lesion preserved in situ in osteoblastic tumors and replaced with a prosthesis in osteolytic tumors.