Radiation therapy for diabetes insipidus caused by Langerhans cell histiocytosis.

Hypothalamic-pituitary radiation therapy has been the standard treatment for the diabetes insipidus of Langerhans cell histiocytosis. The goal of this study was to assess the role of radiation therapy in Langerhans cell histiocytosis-associated diabetes insipidus and to compare the results with nonirradiated controls. Forty-seven patients with pathologically confirmed Langerhans cell histiocytosis were diagnosed with diabetes insipidus between 1950 and 1989 and were treated at the Mayo Clinic. These patients were divided into two groups on the basis of treatment for the diabetes insipidus: The first group (radiation group) included 30 patients (28 of whom were evaluable for response) who received hypothalamic-pituitary radiation therapy, and the second group (control group) included 17 patients who did not. A partial response to treatment was defined as a reduction in vasopressin dosage or improvement in computed tomography (CT) or magnetic resonance imaging (MRI). A complete response was defined as no further need for vasopressin therapy or normalization of CT or MRI. End points analyzed included treatment response, patient characteristics, morbidity, dose-response relationship, and survival. Patient characteristics of the two groups were similar except for age and lung involvement, both of which were significantly less in the radiation group. Thirty-six percent of patients (10 of 28) in the radiation group responded to hypothalamic-pituitary radiation therapy (22% complete response and 14% partial response), whereas none in the control group responded. Five of the six complete responders were irradiated within 14 days of the diagnosis of diabetes insipidus. The mean dose used in the responding and nonresponding patients was 11.2 and 10 Gy, respectively. Three of five patients (60%) treated with more than 15 Gy responded compared to seven of 23 (30%) treated with less than 15 Gy. Eight of the 10 responders (80%), compared to 16 of 35 nonresponders (46%), were female. Only one in 20 patients with concomitant lung histiocytosis responded. Complications of therapy may include insufficiency in other hypothalamic-pituitary axes in the treated patients. Actuarial survivals at 5, 10, 20, and 40 years for the entire group were 80%, 78%, 75%, and 65%, respectively, with a median follow-up in living patients of 14.7 years.