Long-term treatment of 189 acromegalic patients with the somatostatin analog octreotide. Results of the International Multicenter Acromegaly Study Group.

BACKGROUND: We wanted to determine the clinical and biochemical effects of long-term therapy with the somatostatin analog octreotide in 189 acromegalic patients.
METHODS: Patients were treated at 23 medical centers for 6 days to 231 weeks (median, 24.2 weeks) with varying octreotide dosages (100 to 1500 micrograms/d; median, 300 micrograms/d). Serum growth hormone and insulin-like growth factor I (IGF-I) concentrations before and at the end of the study were compared, and correlations between the response to treatment with total daily dosage and duration of treatment were sought.
RESULTS: The clinical response rate was 88%, irrespective of dosage or treatment duration. Serum growth hormone levels decreased in 172 (94%) of 182 patients and IGF-I levels decreased in 91 (92%) of 99. The mean pretreatment growth hormone level was 39.4 +/- 4.4 micrograms/L and decreased to 12.2 +/- 1.5 micrograms/L. Growth hormone levels decreased to less than 5 micrograms/L in 82 (45%) of 182 patients. The pretreatment IGF-I level was 5.62 +/- 0.41 U/mL and decreased to 2.64 +/- 0.19 U/mL; suppression to 2 U/mL or lower occurred in 46 (46%) of 99 patients. The degree of growth hormone suppression was associated with longer treatment duration but not with the total octreotide dosage per day. In 34 patients studied prospectively, pituitary tumor size decreased by greater than 20% in 15 (44%). Side effects occurred in 37% of patients and were most commonly transient loose alcoholic stools, pain at the injection site, and abdominal discomfort; severity was mild to moderate. Glucose tolerance was unchanged or improved in 52% and declined in 48% of 25 patients evaluated.
CONCLUSIONS: Octreotide is an effective treatment for acromegaly that may be used as primary therapy or after surgery and/or pituitary irradiation.