Results of external pituitary irradiation after unsuccessful transsphenoidal surgery in Cushing's disease.

Fourteen adult patients (10 females and 4 males; age range 20-60 years) with persistent Cushing's disease after transsphenoidal microsurgery were treated with pituitary irradiation. Supervoltage multiportal administration was employed at a total dose of 50 Gy (+/- 0.65 SD). The interval between microsurgery and pituitary irradiation was less than 6 months in 6 patients and more than 6 months in 8. The pituitary-adrenal axis was evaluated postsurgically, before irradiation and every 6 months thereafter. The remaining anterior pituitary function was simultaneously tested. Remission rates at 12 months and 24 months after radiotherapy were 61 and 70%, respectively. Two patients developed TSH deficiency and another gonadotropin deficiency during the follow-up after radiation. We conclude that pituitary irradiation is the treatment of choice for persistent Cushing's disease after unsuccessful surgery because of its high efficiency and low incidence of adverse reactions when compared with other forms of treatment.