Efficacy and Safety of 48 Weeks of Treatment with Octreotide LAR in Newly Diagnosed Acromegalic Patients with Macroadenomas: an Open-label, Multicenter, Non-comparative Study

The aim of the present multicentric, open-label, non-comparative study was to evaluate the role of octreotide long-acting repeatable (LAR) as primary therapy for the treatment of GH-secreting pituitary macroadenomas. The patients received octreotide LAR 20 mg every 4 weeks for 12 weeks; afterwards the dose was confirmed or adjusted at 30 mg every 4 weeks, for the remaining 12 weeks, for responder or non-responder patients, respectively. Responder patients continued the study until 48 weeks. Twenty-one naive active acromegalic patients were enrolled. In all patients, GH profile, IGF-I levels and magnetic resonance imaging (MRI) were evaluated at baseline and during treatment. The ability of octreotide LAR to decrease mean GH < 2.5 microg/I and/or normalize IGF-I levels, adjusted for age and gender, was defined respectively as total or partial success. Total success was achieved in 5/21 (23.8%), 6/20 (30%) and 4/14 (28.6%) patients after 12, 24 and 48 weeks; partial success in 7/21 (33.3%), 9/20 (45%) and 9/14 (64%) patients at 12, 24 and 48 weeks according to GH levels, while according to IGF-I levels in 7/21 (33.3%), 7/20 (35%) and 5/14 (35.7%) patients at 12, 24 and 48 week. Tumor size was notably decreased after treatment with octreotide LAR: in 16 macroadenoma patients completing the study, the tumor sizes were 1609 +/- 1288, 818 +/- 616 (49.1 +/- 23.7%) and 688 +/- 567 mm3 (54.6 +/- 24.4%) at baseline, 24 and 48 weeks. This study shows that octreotide LAR is effective in suppressing GH/IGF-I secretion and inducing tumor shrinkage in GH-secreting macroadenomas in a 48-week treatment. Octreotide LAR could be used as primary therapy in patients harbouring large pituitary tumors, who are less likely to be cured by neurosurgery.