Dramatic response with medical treatment of an extensively invasive 'giant' prolactinoma with cabergoline
KS Muralidhara, A Ahmed & D Darko
A previously well 75 year old man, presented with progressive right sided weakness and ataxia of three months duration that had worsened considerably during the previous 3 weeks. On examination, there was right hemiparesis, marked ataxia, sluggish pupillary responses and an extensive right sided visual field deficit confirmed by formal visual field testing. CT brain large suprasellar mass extending into pituitary fossa. MRI brain confirmed it to be a large pituitary macroadenoma with suprasellar and diaphragmatic sellar extension with obstruction of the lateral ventricle and involving the cavernous sinus on the right. Serum Prolactin level was >300,000 mIU/L and random cortisol was <28 nmol/L. Other pituitary hormone levels were normal except for low testosterone (1.5nmol/L). Short synacthen test response was abnormal (<28nmol/L (0 minutes), 234nmol/L(30 min) & 310nmol/L(60min)). Patient was managed medically with cabergoline, titrated up to a dose of 1mg/week. His right sided weakness, ataxia and visual fields showed marked improvement within two weeks of cabergoline therapy and serum prolactin levels showed a steady decrease at 101000mIU/L after one week of therapy, 30,000mIU/L (2 weeks) and 6000mIU/L (3 weeks). Early repeat MRI done four weeks after treatment did not show any significant radiological change in the tumour.
Review of the literature revealed the rarity of such large and invasive prolactinomas. We have reported the case of a patient which highlights the initial absence of symptoms and signs suggesting such a large skull base tumour, as well as the enodocrinological and surgical management dilemmas, due to the risk of life threatening neurological deterioration if medical treatment failed to induce a rapid response. His dramatic response to cabergoline also illustrates the exquisite sensitivity of giant prolactinomas for long acting dopamine agonists. We support using dopamine agonists for the management of giant prolactinomas as first line management in the absence of specific complications that advocate immediate surgical intervention.