INTERSTITIAL IRRADIATION OF BRAIN-TUMORS, USING A MINIATURE RADIOSURGERY DEVICE - INITIAL EXPERIENCE

OBJECTIVE: This report describes the clinical evaluation of a novel st ereotactic radiosurgical device for interstitial irradiation of malign ant brain tumors. METHODS: Fourteen patients with cerebral lesions les s than 3.5 cm in greatest diameter were treated with a single fraction of stereotactic interstitial irradiation (average, 12.5 Gy). Clinical evaluation, Karnofsky Performance Scale ratings, and neuroimaging stu dies were obtained at 6-week intervals postoperatively to assess treat ment response. Reduction or stabilization of tumor size on follow-up i maging was accepted as local control, whereas tumor enlargement indica ted local failure. INSTRUMENTATION: This battery-powered miniature x-r ay generator device produces low-energy x-ray photons that are attenua ted rapidly within tissue. A dose decline rate proportional to 1/r(3) yields extremely sharp dose fall-off curves with minimal exposure to s urrounding tissue. Dose rates of 200 cGy per minute are possible, allo wing for the administration of 12.5 Gy to a lesion 3 cm in diameter in less than 1 hour. RESULTS: Local control (stabilization or reduction in lesion size) was obtained in 10 of the 13 patients with tumors with follow-up of 1.5 to 36 months (mean, 12 mo). Of three patients with r adiographic progression, recurrence was symptomatic in only one. All p atients tolerated the procedure well, and most patients were discharge d home the day after treatment. No new neurological deficits were note d after biopsy and irradiation. CONCLUSIONS: Preliminary experience wi th this novel radiosurgical device has demonstrated its feasibility an d safety. Clinical efficacy of this technique is now under investigati on in an international multicenter study.