Frameless stereotactic radiosurgery with a bite-plate: our experience with brain metastases

Non-invasive frameless stereotactic radiosurgical systems have recently been developed. We report our experience of frameless stereotactic radiosurgery (SRS) with a bite-plate for brain metastases. Between February 2002 and December 2005, 147 patients with brain metastases were treated with C-arm linear accelerator-based SRS and 122 patients were followed up by our institute. An optic tracking system with infrared light-emitting diodes was used for real-time monitoring. A bite-plate with fiducial markers was applied as a first-line method for frameless SRS. Head-ring fixation was used in patients lacking teeth. Lung carcinomas (63%) were the most common primary tumors, followed by breast carcinomas (13%). Ninety patients underwent radiosurgery with a bite-plate and 32 patients underwent fixation of a head ring. Males were significantly more predominant in the head-ring group (26 men and 6 women), compared with the bite-plate group (47 men and 43 women, p < 0.01). The average age (62 years) in the bite-plate group was significantly younger than that (68 years) in the head-ring group (p < 0.01). The median survival time was 12.0 months in the bite-plate group and 8.0 months in the head-ring group (p = 0.0621). Nine patients who had brain metastases in or close to the brain stem were treated with fractionated stereotactic radiotherapy. The frameless stereotactic radiosurgical system with a bite-plate is safe and effective for the treatment of brain metastasis. Elderly male patients sometimes are edentulous and require placement of a head ring for radiosurgery.