Endocrine Abstracts

Objective: Pasireotide is a second-generation somatostatin receptor ligands (SRLs) with highest affinity for somatostatin receptor (SST)5, followed by SST2. It is considered, so far, in patients resistant to first-generation SRLs, after surgical failure. Histological characteristics and T2-weighted MRI can predict resistance to first-generation SRLs in patients with somatotroph adenomas. Previous studies primarily assessed efficacy of pasireotide as 2nd or 3rd line medical treatment. However, pasireotide might be an option in patients expected to be resistant to first-generation SRLs (e.g. hyperintensity T2-weighted MRI signal and/or sparsely granulated immunohistochemical pattern). We describe the efficacy of pasireotide as the first pharmacological treatment.

Methods: Clinical and biochemical parameters, T2-weighted MRI signal intensity, histological diagnosis and efficacy of pasireotide treatment on GH and IGF-1 levels, and tumour volume (by ellipsoid formula), were recorded in four patients (two treated as primary treatment, two after debulking surgery), expected to be resistant to first-generation SRL.

Results: Table 1 presents age, GH and IGF-1 levels, and tumour volume before and after treatment with pasireotide median 5.6 (range 4.5-6.6) months. All tumours were hyperintense on T2-weighted MRI and sparsely granulated somatotroph adenomas were identified in the operated patients. Variability in GH and IGF-1 reduction was observed. Tumour volume decreased at least with 31% and the effect occured early. One patient started ad-on cabergoline therapy two months after pasireotide. At last visit, 18-58 months after treatment initiation, all patients still received pasireotide, two in combination with pegvisomant, one with cabergoline and one patient was additionally treated by radiotherapy. Two patients had normalised IGF-1, two patients further improved IGF-1. HbA1c remained stable in two patients and worsened in two patients with further need of anti-diabetic treatment.

Conclusions: In patients with T2-hyperintense MRI adenomas and presumed resistance to first-generation SRLs, pasireotide may be considered as first line medical treatment, facilitating rapid tumour control and decreased disease activity.