The long-term efficacy of conventional radiotherapy in patients with GH-secreting pituitary adenomas

OBJECTIVE: To assess the long-term efficacy and safety of conventional radiotherapy (RT) in the control of acromegaly according to recent stringent criteria of cure. DESIGN: A retrospective longitudinal study. PATIENTS AND METHODS: Forty-seven patients with active acromegaly were treated with conventional RT between 1982 and 1994. All patients were first operated on and successively irradiated at a dose of 45-50 Gy in 25-28 fractions for persistent (n = 40) or recurrent (n = 7) disease. MEASUREMENTS: Long-term GH/IGF-I secretion and local tumour control were evaluated regularly, and possible side-effects were searched for systematically, especially in terms of secondary endocrine dysfunction. Biochemical cure of acromegaly was defined by glucose-suppressed plasma GH levels below 1 microg/l during an oral glucose tolerance test (OGTT) and normal age-corrected IGF-I values. RESULTS: The 5-, 10- and 15-year overall survival rates were 98%, 95% and 93%, respectively. Suppression of GH during OGTT was seen in 9% of patients at 2 years, 29% at 5 years, 52% at 10 years, and 77% at 15 years. Age-corrected IGF-I levels were normal in 8% of patients 2 years after RT, and this proportion increased to 23%, 42% and 61% after 5, 10 and 15 years, respectively. Normalization of GH/IGF-I mainly depended on pre-RT levels. Local tumour control was 95% at 5, 10 and 15 years after treatment. Late toxicity was mainly represented by progressive hypopituitarism, which was present in 33% of patients at baseline and increased to 57%, 78% and in 85% of patients at 5 10 and 15 years after RT, respectively. CONCLUSION: Conventional RT is effective in the long-term control of GH-secreting pituitary adenomas, although with a high prevalence of progressive hypopituitarism. At present, it remains a suitable option in acromegalic patients uncontrolled by surgery or medical therapy.