THE LONG-TERM OUTCOME OF PITUITARY IRRADIATION AFTER UNSUCCESSFUL TRANSSPHENOIDAL SURGERY IN CUSHINGS-DISEASE

Background Irradiation of the pituitary is widely considered the most appropriate treatment for patients with Gushing's disease in whom tran ssphenoidal microsurgery has been unsuccessful. However, there is litt le information about the long-term efficacy of this treatment. Methods We used external pituitary radiation to treat 30 adult patients with persistent or recurrent Gushing's disease after unsuccessful transsphe noidal surgery. The mean (+/-SD) dose of radiation was 50+/-1 Gy. Pitu itary and adrenal function was assessed every six months after radiati on therapy. Remission was defined as the regression of symptoms and si gns of Gushing's syndrome, normal urinary cortisol excretion, and a lo w plasma cortisol concentration in the morning after the administratio n of 1 mg of dexamethasone at midnight. Results Twenty-five patients ( 83 percent) had remissions during a median follow-up of 42 months (ran ge, 18 to 114). The remissions began 6 to 60 months after radiation th erapy, but in most cases (22 patients) remission occurred during the f irst 2 years. None of the 25 patients had a relapse of Gushing's disea se after remission was achieved. There was no relation between the res ponse to radiotherapy and sex, age, urinary cortisol excretion before radiotherapy, the interval between surgery and radiotherapy, whether a pituitary adenoma was found by pathological examination, or tumor siz e. Seventeen patients had a deficiency of growth hormone after radiati on therapy, 10 had a deficiency of gonadotropins, 4 had a deficiency o f thyrotropin, and 1 had a deficiency of corticotropin. Conclusions Pi tuitary irradiation is an effective and well-tolerated treatment for p atients with Cushing's disease in whom transsphenoidal surgery is unsu ccessful. (C) 1997, Massachusetts Medical Society.