HORMONAL AND RADIOLOGICAL EFFECTS OF MEGAVOLTAGE RADIOTHERAPY IN PATIENTS WITH GROWTH HORMONE-SECRETING PITUITARY-ADENOMA

Nineteen acromegalic patients (12 females and 7 males, aged 24-71 yr) were studied for 1-6 yr after radiotherapy (RT), administered by Xrays (18 MeV) by linear accelerator, with parallel opposite beams (doses 45-50.4 Gy, 1.8 Gy daily). Basal GH levels gradually decreased from 6.3-76.2 mug/L (mean+/-SE, 27.8+/-4.9) to 0.3-43.4 mug/L (11.7+/-3.6 mug/L; p<0.005) at the last assessment. The earliest significant decrease was observed after one yr (14.9+/-3.8 mug/L; p<0.005). Significant changes were observed also in IGF-I values (basal values 1.93-6.85 mU/ml, 3.22+/-0.30; last assessment 0.55-4.57 mU/mL, 1.58+/-0.31; p<0.01). The earliest significant decrease of IGF-I values was observed after 2 yr (1.61+/-0.16 mU/ml; p<0.005). GH levels < 5 mug/L together with normal IGF-I values were observed in 9 patients, 2-4 yr after RT. No changes were observed in PRL values, either in patients with pretreatment normal or elevated PRL levels. The CT and/or MRI picture of macroadenoma disappeared after 6-12 months in 3/12 patients. Moreover, a reduction (20-55%) in the diameter of the adenoma was shown after 6-36 months in other 4 patients. After RT 5/16 (31%) patients required cortisol and 4/19 (21%) thyroid replacement therapy. In 2/3 men a gonadal impairment was shown, that did not occur in the three female patients with normal gonadal function before RT. Using both GH and IGF-I, as hormonal markers, and modern direct radiological techniques, we conclude that RT is highly effective in the treatment of acromegaly.