Forty-one studies were included in the review (1,685 patients). Five studies were retrospective, the rest used a prospective design. Although there were 11 comparative trials, results of comparisons between octreotide and controls were not examined. Double-blinding was reported for only one trial.
There was tumour shrinkage in 53% of patients (95% CI 45 to 61; Ι²=90%), but with very high heterogeneity. This estimate was a little higher when only using MRI (60%; 95% CI 51 to 70) or using more stringent criteria for shrinkage (57%; 95% CI 47 to 67).The mean percentage reduction in tumour size was 37.4% (95% CI 22.4 to 52.4; nine studies).
Higher tumour shrinkage estimates were found in studies that investigated tumour volume rather than linear measurements (OR 2.73; 95% CI 1.73 to 4.31). Estimates were also higher in those treated with intramuscular long acting repeatable (LAR) octreotide rather than subcutaneously (OR 3.18; 95% CI 1.95 to 5.20). There was also higher reported shrinkage in patients receiving treatment for more than a year compared with those receiving for less than a year (OR 1.90; 95% CI 1.02 to 3.55). Studies with a higher proportion of treatment naive patients also found higher shrinkage estimates (test for trend: p<.001). Studies with a higher proportion of patients with safe growth hormone levels found higher shrinkage (test for trend: p<.001).
There was no evidence to indicate publication bias.