Failure of temozolomide and conventional doses of pegvisomant to attain biochemical control in a severe case of acromegaly.

It has been suggested that treatment with adequate dose titration of pegvisomant, a GH antagonist, up to a maximum of 40 mg daily, can achieve IGF-1 normalisation in virtually all patients with acromegaly. On the other hand, temozolomide (TMZ), an alkylating cytostatic agent, has been reported to reduce pituitary tumour size and hormone hypersecretion in a small number of aggressive pituitary macroadenomas. In this paper we report the case of a patient resistant to very high doses of pegvisomant used in combination with somatostatin analogs (SSA) and to TMZ therapy. The patient, initially a 22 year-old man with an invasive GH-secreting pituitary macroadenoma (IGF-1, 371% upper limit of normal), had active acromegaly despite a repeat transsphenoidal surgery followed by radiotherapy and SSA (octreotide 800 μg sc daily) (IGF-1, 262% ULN). In combination with SSA, pegvisomant was started at 20 mg daily and doses were titrated up to 60 mg daily. IGF-1 was moderately reduced and stabilized at 200% ULN after 1 year of treatment. Serum pegvisomant level was 30,500 ng/l, the denaturalized GHBP concentration 1,120 pM and the endogenous GH level was 220 μg/l. Pegvisomant was stopped and TMZ therapy was given for 5 cycles. However, the patient reported an increase of acromegaly symptoms and the serum IGF-1 was raised to the same level prior to pegvisomant therapy. Consequently, pegvisomant was tried again with doses up to 100 mg daily finally resulting in normalisation of serum IGF-1 level and improvement of acromegaly symptoms and patient well-being. We conclude that in some patients with severe acromegaly refractory to multimodal therapy, biochemical control may be difficult to attain with conventional doses of pegvisomant or TMZ therapy.

Citation

Emilie Morin, France Berthelet, John Weisnagel, Martin Bidlingmaier, Omar Serri. Failure of temozolomide and conventional doses of pegvisomant to attain biochemical control in a severe case of acromegaly. Pituitary. 2012 Mar;15(1):97-100

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PMID: 20407837

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