Shrinkage of a PRL-secreting pituitary macroadenoma resistant to cabergoline

Cabergoline decreases both serum PRL levels and size of prolactinomas, incl uding some tumors resistant to other dopamine-agonists. It is common observ ation that the shrinkage of the adenoma is preceded by suppression of PRL l evels. A minority of patients, who do not show a significant decrease of PR L after a short trial with dopamine-agonists, undergoes neurosurgery or rad iotherapy. We report on the case of a 14-year-old girl with a huge prolacti noma who showed, during cabergoline treatment (0.5 mg twice a week), a sign ificant shrinkage of the pituitary mass but no decrease of the very high PR L values. She was referred to us after partial removal of the suprasellar e xtension of the pituitary tumor. The post-surgical evaluation showed very h igh PRL levels (9352 mu g/l; 20941 mu g/l before surgery), which did not de crease during the 2-year treatment with cabergoline (nadir value: 8735 mu g /l). However, one month after the beginning of therapy, MRI showed a signif icant shrinkage of the tumor (tumor volume 5.7 ml, compared with 45.1 ml pr ior to surgery and 24.4 ml after surgery). Subsequently MRIs demonstrated a progressive reduction of the size with a complete disappearance of the sup rasellar and parasellar tissue (tumor volume 1.8, 0.9 and 0.2 ml, at 3, 6 a nd 12 months, respectively). The MRI performed at the 24(th) month showed a secondary empty sella, with residual tumor tissue in the right sphenoidal sinus. Increasing cabergoline, up to 3 mg a week, failed to induce any decr ease of PRL levels. In conclusion, in such macroprolactinomas the shrinkage of tumor is not strictly correlated with (or it is partially dissociated f rom) the inhibition of PRL hypersecretion. The choice of other therapeutic options in cabergoline-resistant macroprolactinomas needs careful neuroradi ological evaluation after a short trial of pharmacological treatment. (J. E ndocrinol. Invest. 22: 306-309, 1999) (C)1999, Editrice Kurtis.