Long-term results of stereotactic gamma knife radiosurgery for pituitary adenomas. Specific strategies for different types of adenoma.

Long-term results of gamma knife radiosurgery for pituitary adenomas are presented and treatment strategies for different adenoma types are discussed. Two hundred and sixty-seven patients with pituitary adenoma have been treated by gamma knife radiosurgery during the past 12 years. There were 131 cases of nonfunctioning and 136 cases of functioning adenomas, in which 71 GH-producing, 33 PRL-producing and 32 ACTH-producing adenomas were included. Retreatment with the gamma knife was done in 8 cases because of large tumors or uncontrolled hormones. Micro- and small adenomas could be cured by gamma knife radiosurgery alone. Surgical or chemical debulking was necessary before radiosurgery for a large tumor with extrasellar extension. Retreatment was effective and safe in some cases. Nonfunctioning adenomas showed higher control rates than functioning adenomas even with lower dose treatment. Cushing disease showed the best response because of the smallest tumor size with the highest dose treatment. Acromegaly and prolactinoma were difficult to control because of larger tumors with lower dose treatment. The rate of hormone normalization was also high in Cushing disease but lower in prolactinoma and lowest in acromegaly. High-dose treatment was necessary for functioning adenomas to control tumor growth and oversecretion of hormones. In conclusion, gamma knife radiosurgery was effective and safe for the treatment of pituitary adenomas. However, the treatment strategies should be specific to each adenoma type according to the radiosensitivity, chemosensitivity and biological nature of the tumor.