Pituitary radiosurgery

The goal of pituitary adenoma radiosurgery is to halt tumor growth, to normalize hormonal hypersecretion if present, and to maintain the performance of normal hypophysis and functionally important structures around the sella-namely, the optic nerve. The minimum distance required between the irradiated target and the optic pathway should be reassessed. For gamma knife model B (or C) the limit should be 2 mm for secreting adenomas and, in the case of nonsecreting adenomas, direct contact could be tolerated when only a short segment of the visual pathway is affected. During the middle of the follow-up period, an antiproliferative effect was achieved in all patients and 70% of adenomas decreased in size usually within 2 years after radiosurgery. Hormonal cure of hypersecreting adenomas is comparable with the results of transsphenoidal microsurgery, apart from the latency, which is usually 2 years. During this period, hypersecretion was arrested in 38% of patients with acromegaly, 90% with Cushing disease, and 54% with prolactinoma. The most important factor influencing postradiation hypopituitarism seems to be the mean dose applied to the hypophysis. The current position of radiosurgery in the majority of cases is as an adjuvant treatment of residual or recurrent adenomas after previous microsurgery. In select cases, radiosurgery may be used as a primary treatment (eg, for patients with contraindications to surgery, for patients in whom the treatment effect is not urgent, and for patients who refuse to undergo open surgery).