Cushing's Disease: Sustained remission in five cases induced by medical therapy with the dopamine agonist cabergoline

The dopaminergic control of Cushing's syndrome

Cushing's Syndrome (CS), or chronic endogenous hypercortisolism, is a rare and serious disease due to corticotroph pituitary (Cushing's disease, CD) and extra-pituitary (ectopic CS) tumours overproducing ACTH, or cortisol-secreting adrenal tumours or lesions (adrenal CS). The first-line treatment for CS is represented by the surgical removal of the responsible tumour, but surgery might be unfeasible or ineffective and medical treatment can be required in a relevant percentage of patients with CS, especially CD and ectopic CS. Corticotroph pituitary and extra-pituitary tumours, as well as adrenal tumours and lesions responsible for CS express dopamine receptors (DRs), which have been found to mediate inhibition of hormone secretion and/or cell proliferation in experimental setting, suggesting that dopaminergic system, particularly DRs, might represent a target for the treatment of CS. Dopamine agonists (DAs), particularly cabergoline (CAB), are currently used as off-label treatment for CD, the most common form of CS, demonstrating efficacy in controlling hormone secretion and tumour growth in a relevant number of cases, with the improvement of clinical picture, and displaying good safety profile. Therefore, CAB may be considered a reasonable alternative treatment for persistent or recurrent CD after pituitary surgery failure, but occasionally also before pituitary surgery, as adjuvant treatment, or even instead of pituitary surgery as first-line treatment in case of surgery contraindications or refusal. A certain beneficial effect of CAB has been also reported in ectopic CS. However, the role of DAs in the clinical management of the different types of CS requires further evaluations.

Effect of cabergoline monotherapy in Cushing's disease: an individual participant data meta-analysis

CONTEXT

The primary treatment of choice for Cushing's disease (CD) is the removal of the pituitary adenoma by transsphenoidal surgery (TSS). The surgical failure is seen in up to 75% of cases depending on the experience of the surgeon in different studies. Medical therapy is one of the options for the treatment of recurrent or persistent CD.

METHODOLOGY

The primary outcome of this meta-analysis was to find the proportion of patients achieving normalisation of 24-h urinary free cortisol (remission of CD) following cabergoline monotherapy. Literature search was conducted in January 2018 in PubMed/MEDLINE database from its date of inception to 31st December 2017. The search strategy used was "[(cushing) OR Cushing's] AND cabergoline". Individual participant data were extracted from the included studies and risk of bias was analysed by review checklist proposed by MOOSE.

RESULTS

The individual participant data of 124 patients from six observational studies were included in this meta-analysis. 92 patients (74.2%) had past pituitary surgery. The proportion of patients achieving remission of Cushing’s disease (CD) with cabergoline monotherapy was 34% (95% confidence interval 0.26–0.43; P = 0.001) [corrected]. The previous surgery [odds ratio (OR) 28.4], duration of cabergoline monotherapy (OR 1.31) and maximum cabergoline dose (OR 0.19) were predictors for remission of CD. Mild and severe side effects were reported in 37.3% and 5.6% of patients, respectively, during cabergoline monotherapy.

CONCLUSIONS

This meta-analysis shows that cabergoline monotherapy is a reasonable alternative for subjects with persistent or recurrent CD after TSS. It can also be used in CD patients either as a bridge therapy while waiting for surgery or in those unwilling for surgery or have contraindication to it.

The Treatment of Cushing's Disease

Cushing's disease (CD), or pituitary-dependent Cushing's syndrome, is a severe endocrine disease caused by a corticotroph pituitary tumor and associated with increased morbidity and mortality. The first-line treatment for CD is pituitary surgery, which is followed by disease remission in around 78% and relapse in around 13% of patients during the 10-year period after surgery, so that nearly one third of patients experience in the long-term a failure of surgery and require an additional second-line treatment. Patients with persistent or recurrent CD require additional treatments, including pituitary radiotherapy, adrenal surgery, and/or medical therapy. Pituitary radiotherapy is effective in controlling cortisol excess in a large percentage of patients, but it is associated with a considerable risk of hypopituitarism. Adrenal surgery is followed by a rapid and definitive control of cortisol excess in nearly all patients, but it induces adrenal insufficiency. Medical therapy has recently acquired a more important role compared to the past, due to the recent employment of novel compounds able to control cortisol secretion or action. Currently, medical therapy is used as a presurgical treatment, particularly for severe disease; or as postsurgical treatment, in cases of failure or incomplete surgical tumor resection; or as bridging therapy before, during, and after radiotherapy while waiting for disease control; or, in selected cases, as primary therapy, mainly when surgery is not an option. The adrenal-directed drug ketoconazole is the most commonly used drug, mainly because of its rapid action, whereas the glucocorticoid receptor antagonist, mifepristone, is highly effective in controlling clinical comorbidities, mainly glucose intolerance, thus being a useful treatment for CD when it is associated with diabetes mellitus. Pituitary-directed drugs have the advantage of acting at the site responsible for CD, the pituitary tumor. Among this group of drugs, the dopamine agonist cabergoline and the somatostatin analog pasireotide result in disease remission in a consistent subgroup of patients with CD. Recently, pasireotide has been approved for the treatment of CD when surgery has failed or when surgery is not an option, and mifepristone has been approved for the treatment of Cushing's syndrome when associated with impairment of glucose metabolism in case of the lack of a surgical indication. Recent experience suggests that the combination of different drugs may be able to control cortisol excess in a great majority of patients with CD.

Adrenocorticotropic Hormone-Dependent Cushing's Syndrome: Use of an octreotide trial to distinguish between pituitary or ectopic sources

OBJECTIVES

Adrenocorticotropic hormone (ACTH) overproduction is usually due to a pituitary tumour which is often not visible on magnetic resonance imaging (MRI). However, ACTH overproduction may be due to an ectopic source. This study aimed to develop a simple non-invasive technique to differentiate these sources.

METHODS

This study took place in King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia, and Sultan Qaboos University Hospital, Muscat, Oman, between 1988 and 2012. Serum cortisol levels were measured in nine patients with ACTH-dependent Cushing's syndrome before and during a 72-hour trial of octreotide. All patients underwent computed tomography (CT) scans. MRI scans were performed on six patients.

RESULTS

CT scans were abnormal in three patients with ectopic ACTH production. MRI scans showed that three patients had pituitary microadenomas. Serum cortisol levels returned to normal in those with confirmed ectopic ACTH production. No response was found in the other six patients.

CONCLUSION

A 72-hour trial of octreotide is recommended for patients with ACTH-dependent Cushing's syndrome and a normal pituitary MRI. This trial will be a useful alternative to petrosal sinus sampling.