Long-term (up to 18 years) effects on GH/IGF-1 hypersecretion and tumour size of primary somatostatin analogue (SSTa) therapy in patients with GH-secreting pituitary adenoma responsive to SSTa

Context The role of somatostatin analogues (SSTa) in the treatment of acromegaly. Objective To evaluate the antihormonal and antitumour efficacy of long-term (up to 18 years) primary treatment with SSTa in patients with GH-secreting pituitary adenoma responsive to SSTa. Design An open, prospective, single-centre, clinical study. Patients Thirty-six acromegalic patients, aged 17-75 years (postoral glucose tolerance test GH > 1 mu g/l, increased IGF-1 for age and sex), were monitored in a single centre and treated with SSTa as first-line therapy. The mean pretreatment GH level was 13.5 +/- 3.1 mu g/l, and IGF-1 (as a percentage of the value over the normal range) was 302 +/- 26%. The patients had macroadenoma (n = 25), microadenoma (n = 8) or empty sella turcica (n = 3). The mean duration of treatment was 8 years (range 3-18 years). Hormonal and morphological monitoring was undertaken after 6 months, and then the patients were followed annually. Results After 1 year, the mean GH and IGF-1 levels had reduced considerably (GH: 2.4 +/- 0.3 mu g/l; IGF-1; 174 +/- 14%, P < 0.01), and they continued to decrease over 10 years, with a mean GH level of 1.6 +/- 0.1 mu g/l and IGF-1 of 123 +/- 18% (P = 0.02). GH < 2 mu g/l, normal IGF-1, or both were observed in 25 (70%), 24 (67%) and 21 (58%) patients, respectively. The mean reduction in tumour volume was 43% (range 13-97%) and shrinkage > 20% was obtained in 21 patients (72%). SSTa treatment was well tolerated with few digestive or metabolic side-effects. Conclusion Long-term (up to 18 years) treatment with SSTa used as first-line therapy is effective from both an antihormonal and antitumour perspective, and is well tolerated in acromegalic patients.