Gamma knife radiosurgery for pituitary adenoma

For the treatment of pituitary adenomas, transsphenoidal surgery is established as a first choice of treatment. However, pituitary adenomas are often not curable with surgery alone, and further treatment including radiation therapy is required to control the disease. In this report, we review the literature of gamma knife radiosurgery for pituitary adenomas and discuss the efficacy of this modern technology. Radiosurgery achieved 85-100% of growth control rates with only mild and transient neurological complications in most cases. Endocrinological normalization was obtained in more than 65% of GH producing tumors. These hormonal control rates seemed to be slightly better in GH producing tumors compared to ACTH producing tumors. To normalize the excessive GH or ACTH levels, radiosurgery for functioning adenomas requires a relatively higher dose, ideally more than 35 Gy at tumor margin. However, the adjacent optic apparatus is less tolerable for irradiation, and the tumors have to be sufficiently separated from it to prevent the radiation-induced visual deficits. Therefore, the role of surgery should not be underevaluated, and even if radiosurgery alone may be able to achieve an excellent outcome in some cases, surgical resection will remain the primary treatment for pituitary adenomas. For high-risk patients or patients with residual tumors after transsphenoidal surgery, gamma knife radiosurgery can be a first choice of treatment, achieving both growth control and hormonal remission with minimum neurological complications, which is equivalent to conventional radiation therapy but with much less risk of radiation injury to the surrounding structures.