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Background: The dopaminergic agonist cabergoline (CAB) has been used in the pharmacological treatment of Cushing's disease (CD). The effect is attributed to the frequent expression of the dopamine receptor subtype 2 in corticotroph tumors. However, in-vivo studies have demonstrated the normalization of 24-h urinary cortisol (24-h UC) in approximately 30-40% of patients over the long term, mainly after surgical failure. The aim was to evaluate the effect of CAB as monotherapy in the early preoperative period and on the recurrence of CD.
Methods: A single-center retrospective study was conducted in a tertiary referral center. Twenty-one patients with confirmed CD were included. The median age was 32 years (13-70), 86% were female, 10 had microadenomas, and 11 had macroadenomas. They were diagnosed from 1986 to 2016 and used CAB as monotherapy either in the preoperative period (N.=7, CABi) or upon recurrence before any other treatment (N.=14, CABr). A "complete response" was considered 24-h UC normalization and a "partial response" was considered a 24-h UC reduction of >50%. UC was obtained at the last follow-up evaluation. The normalization of late-night salivary cortisol (LNSC) after CAB use was evaluated in most patients, as well as the tumor diameter by pituitary MRI, before and after CAB treatment.
Results: Complete response was achieved in 29% (6/21) of subjects after 14.9±16.4 months of treatment, with an average dose of 2.2±1.0 mg/week. Partial response occurred in 9.5% (2/21). LNSC normalized in 35% (6/17) of patients, and no variation in tumor diameter before and after CAB use was observed (N.=13): 6.8±6.8 vs. 7.2±7.1 mm. There was no normalization of 24-h-UC in the CABi subgroup at the end of the treatment, whereas 43% (6/14) of patients in the CABr subgroup reached complete response. The CABi subgroup was treated for 4.7±1.9 months, and the CABr subgroup was treated for 20.1±18.1 months. Both groups were administered similar doses of CAB (CABi 2.1±0.9 and CABr 2.3±1.1 mg/week). Interestingly, the difference between the subgroups' complete response was evident early on in the three months of treatment: no patients in the CABi subgroup vs. 6/10 (60%) in the CABr subgroup (P=0.035), despite a lower dose in the CABr subgroup (1.1 vs. 1.6; P=0.008). The normalization of LNSC occurred in 20% of the CABi subgroup and in 42% of the CABr subgroup.
Conclusions: The normalization of 24-h UC and LNSC occurred in approximately 30% of all patients, mainly in those who used CAB for the recurrence of CD. Despite the small number of subjects in the CABi subgroup, the absence of hormone control in this subgroup discourages the use of this medication as primary therapy or as a preoperative treatment option.
