Somatotropinomas inadequately controlled with octreotide may over-respond to pasireotide: The importance of dose adjustment to achieve long-term biochemical control

Abstract

OBJECTIVE: To present two female patients with acromegaly inadequately controlled with long-acting octreotide who were subsequently treated with the multireceptor-targeted somatostatin analogue pasireotide that over-suppressed IGF-1 levels. METHODS: We report two patients who failed surgery and received long-acting octreotide 20-30 mg/month as part of two double-blind, Phase III clinical trials. After 6-12 months of octreotide treatment, both patients remained inadequately controlled and were switched to long-acting pasireotide 40 mg/month as part of a crossover extension phase. RESULTS: During the core phase of the studies the patients received octreotide 20-30 mg/month, but GH and IGF-1 levels remained above normal. They were switched to pasireotide 40 mg/month after 6 and 12 months, according to the study protocols. After crossover, GH and IGF-1 decreased and normalized, but continued treatment led to further reduction of IGF-1 to below the normal; these reduced levels mildly increased following pasireotide dose reduction to 20 mg/month. Tumour volume was reduced and the clinical signs and symptoms of acromegaly also improved. CONCLUSION: These patients achieved long-term biochemical control, tumour volume reduction and improvement of clinical signs/symptoms after switching from octreotide to pasireotide. IGF-1 over-suppression is observed in a few patients and requires dose adjustment of pasireotide.