Endocrine Abstracts

BACKGROUND: Dopamine agonists are the treatment of choice in macroprolactinomas. A number of these tumours do not respond to the commonly used doses. In such cases the outcome after alternative approaches has not been clarified.

AIM: To assess the response of macroprolactinomas to bromocriptine (BRC) or cabergoline (CAB) and the result of further interventions in resistant cases.

PATIENTS AND METHODS: All records of the patients presenting to Oxford with macroprolactinoma between 1983-2004 were reviewed. Subjects previously operated (with residual tumour <1cm) or previously irradiated or treated with agonists other than BRC/CAB were excluded. The responses (PRL normalization-tumor shrinkage >20%) were evaluated after receiving 7.5 mg BRC/day or 2 mg CAB/week for at least 3 months.

RESULTS: 60 patients [32 males, median age at diagnosis 36 years (16-78)] were identified.

BRC group (n=32, 7 of them initially on 10-30 mg/day): Normal PRL was achieved in 58%(14/24) and tumour shrinkage in 75%(15/20). The relevant rates in patients on initially higher doses were 43%(3/7) and 100%(7/7), respectively. In the 14 non-responsive macroprolactinomas PRL normalization was subsequently achieved in 92%(12/13) by increasing BRC dose (20 mg/day, n=1) or changing to CAB (0.5-1 mg/week, n=4) or by combined approaches (BRC/CAB+TSA, n=2 - BRC/CAB±TSA±RT, n=5). One subject failed to normalize PRL despite CAB(2 mg/week)+TSA+RT (assessed 9 years later).

CAB group (n=28): Normal PRL was achieved in 79%(22/28) and tumour shrinkage in 83%(20/24). In the 6 non-responsive macroprolactinomas PRL normalization was achieved in 67%(4/6) by increasing CAB dose (3-4 mg/week, n=3) or by combined approach (CAB+TSA+RT, n=1). Two subjects failed to normalize PRL despite CAB (3-6 mg/week)+TSA+RT (assessed 3 years later).

CONCLUSIONS: This study shows a successful outcome in the vast majority of resistant macroprolactinomas. Resistant cases may respond either to changes in drug dose/type or to adjuvant treatment (TSA and/or RT). Further controlled studies are required.