Efficacy and limits of somatostatin analogs.

For a considerable time, somatostatin analogs have been the medical therapy of choice for the treatment of acromegaly. In addition to their well-established use as an adjunctive therapy, primary therapy with somatostatin analogs has been investigated in recent years. Adjunctive therapy with octreotide long-acting release over 12-36 months allowed for sufficient GH suppression in 47-75% of patients (average 56%), as summarized by Freda. IGF-I was normalized in 41-75% (average 66%). Tumor shrinkage was observed in about 30% of patients, with a mass reduction of 20-50% in most cases. A bias in some of these studies cannot be excluded, with patients being selected on base of their octreotide responsiveness. Regarding primary treatment of acromegaly with long-acting somatostatin analogs, our review of five published studies, that applied stringent criteria for the analysis of biochemical normalization, revealed sufficient GH and IGF-I suppression in 68% and 61% of the 107 patients included, respectively, and significant tumor reduction in 51%. Therefore, somatostatin analogs represent an effective medical therapy in a significant proportion of patients with acromegaly. Resistance to currently available somatostatin analogs in some patients may be due to reduced density of SSTR2 on the tumors of these patients. New somatostatin receptor ligands with extended binding profile may have even higher efficacy in the biochemical control of patients with acromegaly.