The Efficacy of Octreotide LAR as Firstline Therapy for Patients with Newly Diagnosed Acromegaly is Independent of Tumor Extension: Predictive Factors of Tumor and Biochemical Response

Surgical outcome of acromegaly depends on the preoperatory tumor size and extension. Somatostatin analogues are also a highly effective treatment for acromegalic patients. Nevertheless, the response of GH-secreting adenomas to primary medical therapy is variable. The aim of the present study was to evaluate the efficacy of octreotide LAR as primary therapy for acromegalic patients as a function of initial tumor extension. We performed a multicentre, prospective, observational and analytical study recruiting 19 naive acromegalic patients (5 microadenomas, 10 intrasellar, and 4 extrasellar macroadenomas). All of them were treated with octreotide LAR for 12 months. Basal GH and fasting IGF-I concentrations, and tumor volume were measured at baseline and after 6 and 12 months of treatment. Six patients withdrew the study. The patients who completed the protocol showed a significant reduction of tumor volume (25+/-23%, Wilk's. lambda=0.506, F=4.400, p=0.046) independently of tumor extension at study entry (Wilk's. lambda=0.826, F=0.452, p=0.769). A shrinkage >25% of baseline tumor volume was achieved in 8 (42%) patients with no differences between tumor extension subgroups. Basal GH levels (76+/-18%) and fasting IGF-I (52+/-31%) decreased throughout the study. Six (46%) patients normalized their IGF-I levels. Octreotide LAR is an effective first-line treatment for a large group of acromegalic patients independent of initial tumor extension.