Gamma Knife Surgery of Intrasellar Pituitary Adenomas

Park, Yong Gou; Kim, Dong Seok; Chang, Jin Woo; Chung, Sang Sup

Abstract

In the management of pituitary microadenomas, although transsphenoidal microsurgery presents a very low mortality and morbidity, the high rate of recurrence despite adequate surgical treatment is well known. Stereotactic radiosurgery has been proposed as an alternative treatment modality. Recent advances in neuroimaging permit precise targeting in radiosurgery of microadenomas. Additionally, a prompt hormonal reduction after the treatment is important or the patients with hormonally active microadenomas. The authors performed gamma knife radiosurgery in 22 patients with pituitary adenomas and observed the hormonal changes after radisorugery in 16 patients with functioning microadenomas(4 Cushing's disease, 5 acromegaly, 7 prolactinoma). The maximum dose administered ranged from 35 to 70 Gy. The margin of the tumor was encompassed within the 50 to 90% isodose volume. The endocrinological status was assessed pre- and post-operatively. We used the serum growth hormone, prolactin level, and free cortisol excretion in urine over 24 hours for follow-up evaluation of the patients. The patients, whose hormone levels failed to be reduced to the upper normal range by 10 months following radiosurgery, were regarded as treatment failure. Normalization of hormone level was achieved in eight cases, mostly within 6 months. The other 8 cases showed partial reduction of hormone levels. The reductions were achieved mostly within 1-3 months with some improvement of symptoms. The observation period was not long enough in 5 cases, and the hormone levels in the other 3 cases failed to normalize until 10 months. Although further follow-up is necessary to evaluate the long-term tumor control rate and hormonal effect, these initial results indicate a potential therapeutic role of radiosurgery in controlling hormone hypersecretion in pituitary microadenomas. This form of treatment seems promising in playing an important role in complementing transsphenoidal approach.