[Regrowth pattern of glioblastoma multiforme after radiotherapy]

We investigated the correlation between the technique of radiation therapy used and the regrowth pattern of recurrent glioblastoma multiformes of 48 patients who received initial radiation therapy in our clinic from April, 1974 to March, 1988. Three different techniques have been applied to patients with brain tumors: whole brain irradiation, generous local irradiation (the parallel opposing technique or three field technique, in which the treatment field fully covers the peritumoral low density area on CT images), and restricted local irradiation (the rotation technique, in which the treatment field is restricted to within about 2 cm of the tumor margin on CT images). Radiation dose of the treatment field was over 45 Gy in every case. The regrowth pattern was defined as being one of the followings: inside of the treatment field, outside of the treatment field (this includes the boundary zone between the treatment and the non-treatment field), and remote from the treatment field-which mostly due to the tumor spreading through ventricular systems. In all 7 cases that received whole brain irradiation, tumor recurred inside of the treatment field. Two of these 7 cases showed remote recurrence at the same time. Mean duration time to recurrence was 36.3 weeks. In 27 (90%) of 30 cases that received the generous local irradiation, tumor recurred within the treatment field. Only one showed outside recurrence, and two other cases showed remote recurrence. The mean duration time to recurrence in this group was 32.2 weeks. Of 11 cases that received restricted local irradiation, 3 cases (27%) showed recurrence outside of the treatment field, one showed recurrence in a remote area. The mean duration time to recurrence in this group was 38.3 weeks, but was not significantly longer than that of other two groups. These results indicate that restricted local irradiation sometimes fails to cover the tumor invaded area, and that the results of treatment using generous local irradiation are almost the same as those using whole brain irradiation. This suggests that generous local irradiation is advantageous to patients with brain tumors since the incidence of subacute side effects such as mental deterioration is much lower in local irradiation as compared with whole brain irradiation.