Pasireotide: successful treatment of a sparsely granulated tumour in a resistant case of acromegaly

Abstract

The granulation pattern of somatotroph adenomas is well known to be associated with differing clinical and biochemical characteristics, and it has been shown that sparsely granulated tumours respond poorly to commonly used somatostatin receptor ligands (SRLs). We report a challenging case of acromegaly with a sparsely granulated tumour resistant to multiple modalities of treatment, ultimately achieving biochemical control with pasireotide. A 26-year-old lady presented with classical features of acromegaly, which was confirmed by an oral glucose tolerance test. Insulin-like growth factor 1 (IGF1) was 1710 μg/L (103–310 μg/L) and mean growth hormone (GH) was >600 U/L. MRI scan showed a 4 cm pituitary macroadenoma with suprasellar extension and right-sided cavernous sinus invasion. She underwent trans-sphenoidal pituitary surgery. Histology displayed moderate amounts of sparsely granular eosinophilic cytoplasm, staining only for GH. Postoperative investigations showed uncontrolled disease (IGF1:1474 μg/L, mean GH:228 U/L) and residual tumour in the cavernous sinus. She received external beam fractionated radiation. Over the years, she received octreotide LAR (up to 30 mg), lanreotide (up to 120 mg) two weekly, cabergoline, pegvisomant and stereotactic radiosurgery to no avail. Only pegvisomant resulted in an element of disease control; however, this had to be stopped due to abnormal liver function tests. Fifteen years after the diagnosis, she was started on pasireotide 40 mg monthly. Within a month, her IGF1 dropped and has remained within the normal range (103–310 μg/L). Pasireotide has been well tolerated, and there has been significant clinical improvement. Somatostatin receptor subtyping revealed a positivity score of two for both sst5 and sst2a subtypes.