PITUITARY TUMOR TYPE AFFECTS THE CHANCE OF BIOCHEMICAL REMISSION AFTER RADIOSURGERY OF HORMONE-SECRETING PITUITARY ADENOMAS

Reported biochemical remission rates have ranged widely after stereotactic radiosurgery for patients with hormone-secreting pituitary adenomas. Confounding variables include histology, radiation dose, use of pituitary-suppressive medications, and length of follow-up.A retrospective review of 46 patients with pituitary adenomas (growth hormone-secreting, n = 27; prolactin-secreting, n = 11; adrenocorticotropin-secreting, n = 8) undergoing radiosurgery between January 1990 and December 2003 was conducted. All received a tumor margin dose of 18 Gy or more and were off pituitary-suppressive medications for at least 1 month before radiosurgery. The groups were similar with regard to irradiated volume, radiation dose, and follow-up. The median endocrinological follow-up after radiosurgery was 54 months.The 4-year remission rates were 87% for patients with Cushing's disease, 67% for patients with acromegaly, and 18% for patients with prolactinomas. Patients with oversecretion of adrenocorticotropin or growth hormone were more likely to achieve remission after radiosurgery than patients with prolactinomas (hazard ratio, 4.4; 95% confidence interval, 1.1-18.2; P = 0.04). Of 44 patients with normal or partial anterior pituitary function before radiosurgery, 16 (36%) developed one or more new anterior pituitary deficits. The incidence of new anterior pituitary deficits was 26% at 4 years. No differences were noted in the incidence of new anterior deficits among the groups.There seems to be a differential sensitivity after radiosurgery for hormone-secreting pituitary adenomas. Remission rates are greater for patients with Cushing's disease and acromegaly, whereas radiosurgery is less effective in achieving biochemical remission for patients with prolactinomas.