Intraoperative radiation therapy for brain tumors with emphasis on retreatment for recurrence following full-dose external beam irradiation.

We performed intraoperative radiotherapy (IORT) in 19 patients with various brain tumors. IORT was given for primary tumors in 2 patients with malignant glioma, but was used for treating recurrent tumors in the other 17 patients. The former 2 patients respectively received 33 Gy by IORT alone and 30 Gy by IORT in combination with 50 Gy of external beam radiotherapy (EBRT), and survived for 12 and 9 months. The latter 17 patients had received EBRT at 4 to 112 months before IORT. In this group, single doses of 23-40 Gy were delivered by IORT after removing as much tumor as possible. The median survival time after IORT was 12 months for 9 patients with glioblastoma or anaplastic astrocytoma, while it was 51 months for 8 patients with less infiltrative tumors (ependymoma, anaplastic ependymoma, and anaplastic oligodendroglioma). One patient with ependymoma and another with anaplastic ependymoma are currently alive with no evidence of disease at 7 and 11 years after IORT, respectively. Symptomatic brain necrosis occurred in 3 patients following IORT, but the symptoms were relieved in 2 of them by the removal of necrotic brain tissue. It is concluded that IORT combined with extensive tumor removal has an acceptable toxicity in previously irradiated patients and can be effective for selected recurrent malignant brain tumors.