Management of dopamine agonist-resistant prolactinoma

Dopamine agonists are usually very effective in the treatment of prolactinomas. Nonetheless, a subset of individuals does not respond satisfactorily to these agents and this resistance is characterized by failure to achieve normoprolactinaemia and a 30% or more reduction in maximal tumor diameter (in the case of macroprolactinoma) under maximally tolerated doses. Its overall prevalence is 20-30% for bromocriptine (BRC) and around 10% for cabergoline (CAB). The two main predictive factors are male gender and tumor invasiveness. The management of drug-resistant prolactinomas includes several options. Any BRC-resistant patient should be switched to CAB which will normalize prolactin in 80% of them. As long as adverse effects do not develop, dose escalation of CAB is reasonable, with the expectation that subsequent dose reduction will be possible. Echocardiographic monitoring is advised in such patients because of the potential association with cardiac valvular fibrosis. Also, maintaining maximal CAB doses at 3.5 mg/week may lead to progressive hormonal control in a significant proportion of patients. Complete resistance to CAB is infrequent. In a study of 122 patients with a macroprolactinoma, only 7 (6%) could not achieve control despite maximal CAB doses for more than 12 months. A large resistant prolactinoma is also an indication for transsphenoidal neurosurgery, aiming at a debulking which may improve postoperative medical control. For patients who harbor aggressive prolact...
Source: Neuroendocrinology - Category: Endocrinology Source Type: research