Resistant Paediatric Somatotropinomas due to AIP Mutations: Role of Pegvisomant.

BACKGROUND

Somatotropinomas are rare in childhood and frequently associated with genetic mutations. AIP mutations are found in 20-25% cases and cause aggressive somatotropinomas, often resistant to somatostatin analogues.

AIMS

To assess responses to multimodal therapy including pegvisomant in 2 children with sporadic somatotropinomas due to AIP mutations.

CASE DESCRIPTION

We report 2 children, a boy aged 13 and a girl aged 10, with rapid growth, visual impairment, and growth hormone hypersecretion. Magnetic resonance imaging confirmed a pituitary macroadenoma with parasellar extension in both. Despite multiple surgical attempts to debulk tumour mass, residual tumour persisted. Genetic analysis showed two different AIP mutations (patient 1: c.562delC [p.Arg188Glyfs*8]; patient 2: c.140_ 163del24 [p.Gly47_Arg54del8]). They were initially treated with a long-acting somatostatin analogue (octreotide LAR 30 mg/month) and cabergoline as a dopamine agonist, with the later addition of pegvisomant titrated up to 20 mg/day and with radiotherapy for long-term control. Somatostatin analogue was ceased due to patient intolerance and lack of control. Patient 1 had normalization of insulin-like growth factor-1 (IGF-1) after 5 months of combined therapy with pegvisomant and cabergoline. For patient 2, normalization of IGF-1 was achieved after 2 months of cabergoline and pegvisomant.

CONCLUSION

AIP-associated tumours can be resistant to management with somatostatin analogues. Pegvisomant can safely be used, to normalize IGF-1 levels and help control disease.