Endocrine Abstracts

Background: Cabergoline (CAB) is the most effective dopamine agonist (DA) used for the treatment of macroprolactinoma. Few data on the dose of CAB necessary for achieving and maintaining normal prolactin (PRL) levels are available. We aimed to study these parameters in a large series of patients with macroprolactinomas

Methods: We retrospectively analysed the clinical, biochemical and imaging features at diagnosis and the treatment response to CAB (dose necessary for normalizing and thereafter for maintaining normal PRL levels on long term) in 260 patients (125F) with macroprolactinomas followed at the Service d′Endocrinologie et des Maladies de la Reproduction in Hôpital Bicetre Hospital, Le Kremlin-Bicêtre, France.

Results: At diagnosis, the median [min; max] age, PRL level and maximal tumor diameter was 32.7 [10.6; 83.1] years, 680 [6; 38000] ng/ml and 20 [10; 110] mm, respectively. PRL levels were normalized in 68.4% of patients under CAB treatment. Weekly mean (SD) CAB dose necessary for normalizing and thereafter for maintaining normal PRL levels were 1.30 (1.02) and 0.74 (0.62) mg (P≤1.10⁻⁴), respectively. CAB dose de-escalation was tried in 84 (53.5%) of the 153 patients in whom CAB succeeded to normalize PRL levels. This dose de-escalation was successful in 77 out of 84 patients (91.7%). The main differences between patients in which dose de-escalation was tried and the others are the duration of CAB treatment (P≤1.10⁻⁴), the duration between the introduction of CAB and the time of PRL normalization (P=0.05) and the tumor volume at time of PRL normalization (P=0.02).

Conclusion: The dose of CAB necessary for maintaining normal PRL level on long term is lower than the dose necessary for normalizing PRL levels. Dose de-escalation after normalization of PRL levels is possible and potentially useful when considering the potential side effects of the drug which depends on its cumulative dose.