Exposure time and frequency of irradiation in brain tumours

The survival of a group of patients with malignant gliomas of the brain submitted to radical surgery and radiotherapy was studied. The average survival was nearly 4 times longer with X-ray treatment than with cobalt 60 irradiation when a comparison was made between 24 patients with glioblasto-astroblastoma (grade 3-4) who received one or the other type of treatment (12 patients in each group). These results are ascribed to the fact that the daily exposures to X-ray were much longer than with cobalt and so, during those prolonged sessions, a greater number of tumour cells could be destroyed as they successively reached the pre-mitotic period of enhanced vulnerability to radiation. A smaller group of patients irradiated with linear accelerators fared worse than those who received X-ray treatment. Changes to the parameters of irradiation used at the present time with cobalt units or linear accelerators are suggested.