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

Summary 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 µg/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.