Conventional pituitary irradiation is effective in normalising plasma IGF-I in patients with acromegaly

Objective: For patients in whom acromegaly persists despite pituitary surgery, conventional pituitary irradiation represents an additional treatment option. A 30-60% cure rate is described in the literature, but these studies did not utilise strict rules of remission, such as 'safe' GH levels <2.5 <mu>g/l, and age-adjusted normal IGF-I levels. Design and methods: We report the outcome of 41 patients with acromegaly who received pituitary conventional external irradiation. The median follow-up time was 12.8 years (3.7-43.4 years) post-radiotherapy. Results: The median pre-irradiation GH level was 31.0 mug/l (7.0-210 mug/l). Information on IGF-I levels was only available for 6 patients prior to therapy. Utilising strict rules of remission, one-third (14/41) of our patients had normal biochemical parameters, i,e. 'safe' GH (0.5 mug/l (range 0.2-1.6 mug/l)) and normal age-adjusted IGF-I levels (multiple of upper limit of normal range (xULN): 0.45 (0.2-1.0)) at the end of the follow-up period. An additional 9 patients achieved normal levels with adjunctive drug therapy. Furthermore, disease activity was reduced in a considerable proportion of the 18 patients who did not achieve normal biochemical levels (CH: 3.6 mug/l (1.9-15.7 mug/l): xULN of IGF-I: 1.6 (0.9-2.6)), In retrospect, remission is unlikely in patients who had a GH level greater than 52 mug/l (mean+2 S.D. of cured patients) prior to radiotherapy. In addition to the 12 patients with pre-irradiation pituitary functional deficiency, another 11 patients developed symptoms of panhypopituitarism during the 3-year period following irradiation. Within a 6-year period. partial pituitary insufficiency was observed in a further 7 patients, thus necessitating hormone substitution treatment. Conclusion: Using strict rules of remission, in our cohort we found both a normalisation of IGF-I and safe GH levels in 34%, of patients treated for acromegaly with conventional irradiation therapy.