[Histological studies of the effect of intra-operative irradiation on osteosarcoma]

At the Department of Orthopaedic Surgery of Kyoto University Hospital, intra-operative radiotherapy by the high dose electron irradiation has so far been used in treating patients with osteosarcoma. The dose distribution was calculated by CT-number so that the focus was subject to at least 80% of the irradiation doses and the surgically opened lesion was irradiated with 5,000 rad of 12-26 MeV electron beams. In order to accurately assess its therapeutic effect, histological studies were conducted on 9 patients who underwent en bloc resection or amputation following irradiation treatment for osteosarcoma. Method The excised specimen was sagittally cut in half and was fixed in 10% neutral buffered formalin. The specimen was cut into 5 mm thick sections corresponding to CT cross sections. At the border region between irradiated and non-irradiated fields, specimens were prepared using sagittal sections to compare the histological findings of both fields. After all specimens were carefully macroscopically examined and then photographed with soft-X-ray film, some of them were prepared as non- delimed specimens in polyester resin and were observed by contact microradiography and fluorescent microscopy. The remaining specimens after deliming in Plank - Rychlo solution were sliced to 4-8 micron thick for study as large specimen stained with hematoxylin and eosin. Four patients had been administered tetracycline 3 days preoperatively. Results Histologically the changes of the specimens were evaluated using the Oohoshi and Shimosato 's criteria for the histological effects of irradiation. In two of the 9 patients, who had received unidirectional irradiation, the survival of Grade 2a-2b tumor tissue was observed in the superficial layers both inside and outside the periosteum. Six patients who were irradiated from both sides or three directions, showed complete necrosis in extremely small areas of Grade 2b-3 change of tumor cells. Only one of these 9 patients had a local recurrence after the irradiation. Marked fluorescence was observed in the recurrent tissue by tetracycline labeling, but no fluorescence was observed in any of the other cases in the tumorous tissues which had fallen within the range of irradiation. These findings strongly suggest that intra-operative irradiation is extremely effective in controlling local osteosarcoma lesion in the extremities.