Stereotactic single high dose radiation therapy of benign intracranial meningiomas.

Seventeen patients with intracranial meningiomas were treated with single high dose irradiation at the German Cancer Research Center in Heidelberg. Indications for radiosurgery included unresected tumors, gross disease remaining despite surgery, and recurrences. Therapy was carried out by a technique using multiple non-coplanar arc irradiations from a 15 MeV linear accelerator. This technique coupled with secondary tungsten collimators allowed a high concentration of the dose in the target volume with an extremely steep dose gradient at the field borders. The patients were treated with a single irradiation dose ranging from 10 to 50 Gy (mean of 29 Gy). Four of 17 patients died: one death was tumor-related and not attributable to the treatment, one died of a treatment related complication, and two patients died of intercurrent diseases. The remaining 13 of the 17 patients with a median follow-up time of 40 months have no evidence of tumor relapse. Late severe side effects include five patients with a large area of brain edema, three of which were concurred with tumor necrosis. We conclude from these initial data that single high doses of irradiation concentrated to the tumor volume by stereotaxic methods can achieve local tumor control. It is also clear from these data that the effective therapeutic dose range must be better defined.