Treatment of Cushing's disease with low dose radiation therapy.

Nineteen patients with Cushing's disease were treated with low dose external pituitary irradiation (20 Gy (2000 rad) in eight fractions over 10 days). While awaiting the effects of pituitary irradiation all patients were treated with metyrapone. Seven patients had a complete remission of their disease within six to 12 months of irradiation. They did not require any further treatment and were followed up for a mean of three and a half (range one to eight) years. Another patient had a complete remission after a second course of pituitary irradiation. A further two patients showed a significant biochemical improvement after irradiation, although they were not rendered eucorticoid. There were no complications after this dose of irradiation. These results compare favourably with those reported after pituitary irradiation at conventional doses (40-50 Gy (4000-5000 rad) over four or five weeks) but were not associated with any complications. It is therefore recommended that low dose external pituitary irradiation be used as definitive first line treatment for Cushing's disease.