Usefulness and safety of pasireotide in a case of acromegaly highly resistant to treatment.

Background: Pasireotide is a novel somatostatin analogue with higher affinity to 4/5 known human somatostatin receptors subtypes. It could have utility in acromegalic patients not responding to available treatments, although a deterioration in glucose metabolism is described during its use. Case: We describe our experience in the management of a case of a 41 years-old man affected by mixed GH-PRL secreting pituitary macroadenoma (32 mm) high resistant to different treatments. At baseline, the patient showed GH nadir after OGTT 26 ng/ml, IGF-1 1369 ng/dl, PRL 2386 ng/ml, normal glucose tolerance (NGT) with HbA1c 5.9%. Eight months of pre-operative treatment with monthly lanreotide LA 120 mg and weekly cabergoline 0,5-1 mg were ineffective in improving biochemistry and tumor mass (GH nadir 45 ng/dl, IGF-1 908 ng/ml, PRL 589 ng/ml; tumor mass 30 mm), but have slightly worsened the GT (IFG + IGT, with HbA1c 6,8%). After surgery, no significant improvement was achieved (GH nadir 12 ng/dl, IGF-1 952 ng/ml, HbA1c 6.1%, unchanged tumor mass). After 9 months of poor response to monthly octreotide LAR 30 mg and weekly cabergoline 1.5-2.0 mg (GH nadir 15 ng/dl, IGF-1 758 ng/ml, PRL 201 ng/ml; tumor mass 28 mm, IFG + IGT with HbA1c 6.5%) and 6 months of the daily dose of pegvisomant 10-15 mg (IGF-1 655 ng/ml, unchanged tumor mass, IFG with HbA1c 6.1%), pasireotide LAR was started 5 months ago at the monthly dose of 40 mg. To date, a slight not complete biochemical response was obtained (GH nadir 9 ng/dl, IGF-1 408 ng/ml, PRL 41 ng/ml, tumor mass 25 mm) but an unexpected improvement in GT was shown (NGT, with HbA1c 6.0%), likely related to the trend of reduction in GH levels. Conclusion: Pasireotide could be a useful therapeutic option in acromegaly not necessarily associated with a worsening in glucose metabolism.