[The results of gamma knife radiosurgery for malignant skull base tumors]

The results of gamma knife radiosurgery for malignant skull base tumors were analyzed using repeated magnetic resonance imagings and neurological examinations. Nineteen malignant skull base tumors were treated and followed up for 22.3 months (5-40 months) using MR imagings. The mean age was 54.4 years old (ranging from 16-85). Ten were male and 9 were female. Prior to the radiosurgery, removal of the tumors in 17 cases, conventional radiation therapy in 7, and chemotherapy in 4 etc. were performed. The pathological diagnoses were chordoma in 6 cases, metastatic tumors in 5, epipharyngeal carcinoma in 2, adenoid cystic carcinoma in 2, and others in 4. The locations of tumors were the clivus in 8, the parasellar region in 5, the epipharynx in 2, the paranasal sinus in 2, C-P angle in 1, and intraorbital region in 1 (14 were intracranial and 5 were extracranial). The mean diameter of the tumor was 33.5mm. The mean maximum dose was 26.8Gy and the mean marginal dose was 12.9Gy during treatment. Repeated MR imagings revealed decrease of tumor size in 12 cases, no change in 1, and increase of tumor size in 5 (unknown in 1). Follow-up neurological examinations showed improvement in 3 cases, no change in 9, and deterioration in 7. There were 11 deaths during a mean follow-up period of 17.8 months (5-32 months) and another 8 cases are alive for a mean follow-up of 30.5 months (20-40 months) after the radiosurgery. Although the tumor size was large at the time of treatment, the results of gamma knife radiosurgery were promising. Considering the quality of life of patients with malignant skull base tumors, it is emphasized that gamma knife treatment is the method of choice compared with radical removal of the tumors.