[Use of cabergoline in persisting Cushing's disease]

Effectiveness of Medical Treatment of Cushing's Disease: A Systematic Review and Meta-Analysis

Objective

The objective of this systematic review was to evaluate the effectiveness and safety of pasireotide, cabergoline, ketoconazole, levoketoconazole, metyrapone, osilodrostat, and temozolomide for the treatment of Cushing's disease (CD).

Methods

The primary outcomes were the proportion of CD control, adverse events (AE), and reduction of urinary free cortisol. Search strategies were applied to Embase, Medline, and CENTRAL. Independent reviewers assessed the study eligibility, extracted data, and evaluated risk of bias. Standardized mean difference was calculated with 95% confidence interval (CI) for continuous data (i.e., pre- and post-intervention). Random meta-analyses for the proportion of CD control and AE were conducted.

Results

Twenty-nine controlled and non-controlled studies were included. No study with temozolomide and levoketoconazole and one study with osilodrostat fulfilled the inclusion criteria. The meta-analyses of proportion of CD control was 35% for cabergoline (95% CI: 27-43%, six studies, 141 participants), 44% for pasireotide (95% CI: 25-35%, eight studies, 522 participants), 41% for ketoconazole (95% CI: 36-46%, six studies, 450 participants), 66% for metyrapone (95% CI: 46-87%, four studies, 66 participants), and of 66.4% for osilodrostat (95% CI: 57.9, 74.3, 97 participants, one study). One study compared two different treatments (cabergoline vs. ketoconazole), and no statistical difference was observed in CD control (RR: 0.53, 95% CI: 0.15 to 1.87, 14 participants, very low certainty of evidence). The most frequent AE associated with pasireotide was hyperglycemia, dizziness and nausea with cabergoline and metyrapone, and elevated transaminases with ketoconazole.

Conclusion

The superiority of one drug over another could not be determined due to lack of controlled studies, but the proportion of disease control identified in our meta-analysis may support clinical decision. New therapeutic options should be investigated due to the limited efficacy and tolerability of the currently available medical treatment for patients with Cushing's disease.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020205567, identifier CRD42020205567.

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.

Current strategies for the treatment of severe Cushing's syndrome

Severe Cushing's syndrome may present an acute emergency in patients diagnosed with Cushing's syndrome with recent onset of at least one of the following: sepsis, opportunistic infection; intractable hypokalaemia, uncontrolled hypertension; heart failure; gastrointestinal hemorrhage; acute psychosis; progressive debilitating myopathy; thromboembolism; uncontrolled hyperglycemia and ketoacidosis. The biochemical definition includes serum cortisol ≥41μg/dl (1100 nmol/l) and/or severe hypokalemia (<3.0 mmol/l) or urine free cortisol fivefold the upper limit of normal. Treatment focuses on the management of severe metabolic disturbances followed by rapid resolution of the hypercortisolemia and subsequent confirmation of the cause. We emphasize the control of the hypokalemia, hypertension, diabetes and any psychotic state, anti-coagulation, monitoring and vigorous therapy of opportunistic infections. The ideal first-line therapies include metyrapone and ketoconazole, followed by parenteral etomidate; if all else fails life-saving bilateral adrenalectomy should be considered.

Current approaches to the pharmacological management of Cushing's disease

If treatment of Cushing's disease (CD) by surgery is not successful, medical therapy is often required. Long-term use of metyrapone is limited by hirsutism and hypertension and escape because of increased ACTH levels. Although ketoconazole can normalize cortisol levels in 50%, liver toxicity limits its use. Mitotane, an adrenolytic agent, has had minimal use for benign disease. Etomidate is useful when rapid reduction in cortisol levels is needed. Cabergoline can normalize cortisol levels in CD in about one-third of patients and is well tolerated. Pasireotide can normalize cortisol levels in CD in about 25% but causes worsening of glucose tolerance in most patients. Mifepristone, a blocker of cortisol receptors, improves clinical aspects of CD in most patients but cortisol and ACTH measurements do not reflect clinical activity and adrenal insufficiency, hypokalemia, and endometrial hyperplasia can occur. Combinations of drugs can be tried in patients resistant to monotherapy.

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

We report five cases of Cushing's disease where the patients were given a therapeutic trial of cabergoline. Morning serum cortisol, adrenocorticotrophic hormone (ACTH), and sleeping cortisol concentrations were significantly raised. Magnetic resonance imaging (MRI) scans revealed pituitary microadenomas in 3 patients but were normal in the others. Ectopic ACTH production was excluded in the 2 patients with normal MRI scans. All were given a therapeutic trial of cabergoline (1 mg daily). Four patients responded with a prompt fall in serum cortisol levels and had a sustained clinical and biochemical remission for 378, 44, 28 and 14 days, respectively. One patient failed to respond. In conclusion, we suggest that all patients with Cushing's disease should undergo a therapeutic trial of cabergoline. Responders can then be prepared for surgery or, if needed, treated medically in the long term.

Efficacy of cabergoline in uncured (persistent or recurrent) Cushing disease after pituitary surgical treatment with or without radiotherapy

OBJECTIVE

To evaluate the efficacy of cabergoline therapy in patients with Cushing disease who remained uncured (had persistent or recurrent disease) after a pituitary surgical procedure with or without radiotherapy.

METHODS

We undertook a prospective, open-label, single-arm study, with short-term (5 months) and longterm (1 year) evaluations. In 20 patients with uncured Cushing disease, treatment was initiated with cabergoline at a dosage of 1 mg/wk, with a monthly increment of 1 mg, until midnight serum cortisol (MNSC) or low-dose dexamethasone suppression serum cortisol (LDSC) (or both) normalized or a maximal dosage of 5 mg/wk was reached.

RESULTS

Overall, 5 of 18 patients (28%) responded in terms of LDSC or MNSC (or both) at a mean dosage of 3.6 mg/wk (range, 2 to 5). When the response was defined with use of either LDSC or MNSC level as an isolated criterion, it was achieved in 4 of 16 patients (25%) and 3 of 18 patients (17%), respectively. Four patients were treated for 1 year, and the response was persistent in 2 and 3 patients on the basis of MNSC and LDSC levels, respectively. Lower baseline serum cortisol (basal, MNSC, and LDSC) values were predictive of a therapeutic response.

CONCLUSION

Cabergoline was an effective therapy in 28%, 25%, and 17% of patients with uncured Cushing disease in terms of LDSC or MNSC (or both), LDSC alone, and MNSC alone, respectively. Further studies are needed to address the persistence of the drug response and the effects on the dynamics of the hypothalamic-pituitary-adrenal axis.

Cabergoline monotherapy in the long-term treatment of Cushing's disease

BACKGROUND

Cabergoline is a long-acting dopamine receptor agonist used to treat prolactinomas. Identification of D(2) receptors in corticotroph tumors led to clinical trials of cabergoline therapy in limited cases of Nelson's syndrome, ectopic ACTH-secreting tumors, and recently Cushing's disease (CD).

OBJECTIVE

To evaluate the long-term efficacy of cabergoline monotherapy in patients with CD.

METHODS

Retrospective analysis of non-randomized clinical therapy with cabergoline in 30 patients with CD treated in academic centers of Buenos Aires and Montreal. Cabergoline was initiated at 0.5-1.0 mg/week and adjusted up to a maximal dose of 6 mg/week based on urinary free cortisol (UFC) levels. Complete response to cabergoline was defined as a sustained normalization of UFC with at least two normal values measured at 1-3 months interval; partial response was defined as a decrease of UFC to <125% of the upper limit of normal, and treatment failure as UFC ≥ 125% of it.

RESULTS

Within 3-6 months, complete response was achieved in 11 patients (36.6%) and partial response in 4 patients (13.3%). After long-term therapy, nine patients (30%) remain with a complete response after a mean of 37 months (range from 12 to 60 months) with a mean dose of 2.1 mg/week of cabergoline. Two patients escaped after 2 and 5 years of complete response, but one patient transiently renormalized UFC after an increase in cabergoline dosage. No long-term response was maintained in four initial partial responders.

CONCLUSIONS

Cabergoline monotherapy can provide an effective long-term medical therapy for selected patients with CD, but requires close follow-up for dose adjustments.

Treatment of Cushing disease: overview and recent findings

Endogenous Cushing syndrome is an endocrine disease caused by excessive secretion of adrenocorticotropin hormone in approximately 80% of cases, usually by a pituitary corticotroph adenoma (Cushing disease [CD]). It is a heterogeneous disorder requiring a multidisciplinary and individualized approach to patient management. The goals of treatment of CD include the reversal of clinical features, the normalization of biochemical changes with minimal morbidity, and long-term control without recurrence. Generally, the treatment of choice is the surgical removal of the pituitary tumor by transsphenoidal approach, performed by an experienced surgeon. Considering the high recurrence rate, other treatments should be considered. Second-line treatments include more radical surgery, radiation therapy, medical therapy, and bilateral adrenalectomy. Drug treatment has been targeted at the hypothalamic or pituitary level, at the adrenal gland, and also at the glucocorticoid receptor level. Frequently, medical therapy is performed before surgery to reduce the complications of the procedure, reducing the effects of severe hypercortisolism. Commonly, in patients in whom surgery has failed, medical management is often essential to reduce or normalize the hypercortisolemia, and should be attempted before bilateral adrenalectomy is considered. Medical therapy can be also useful in patients with CD while waiting for pituitary radiotherapy to take effect, which can take up to 10 years or more. So far, results of medical treatment of CD have not been particularly relevant; however, newer tools promise to change this scenario. The aim of this review is to analyze the results and experiences with old and new medical treatments of CD and to reevaluate medical therapies for complications of CD and hypopituitarism in patients with cured CD.

Somatostatin and dopamine receptors as targets for medical treatment of Cushing's Syndrome

Somatostatin (SS) and dopamine (DA) receptors are widely expressed in neuroendocrine tumours that cause Cushing's Syndrome (CS). Increasing knowledge of specific subtype expression within these tumours and the ability to target these receptor subtypes with high-affinity compounds, has driven the search for new SS- or DA-based medical therapies for the various forms of CS. In Cushing's disease, corticotroph adenomas mainly express dopamine receptor subtype 2 (D(2)) and somatostatin receptor subtype 5 (sst(5)), whereas sst(2) is expressed at lower levels. Activation of these receptors can inhibit ACTH-release in primary cultured corticotroph adenomas and compounds that target either sst(5) (pasireotide, or SOM230) or D(2) (cabergoline) have shown significant efficacy in subsets of patients in recent clinical studies. Combination therapy, either by administration of both types of compounds separately or by treatment with novel somatostatin-dopamine chimeric molecules (e.g. BIM-23A760), appears to be a promising approach in this respect. In selected cases of Ectopic ACTH-producing Syndrome (EAS), the sst(2)-preferring compound octreotide is able to reduce cortisol levels effectively. A recent study showed that D(2) receptors are also significantly expressed in the majority of EAS and that cabergoline may decrease cortisol levels in subsets of these patients. In both normal adrenal tissue as well as in adrenal adenomas and carcinomas that cause CS, sst and DA receptor expression has been demonstrated. Although selected cases of adrenal CS may benefit from sst or DA-targeted treatment, its total contribution to the treatment of these patients is likely to be low as surgery is effective in most cases.

Pituitary-directed medical treatment of Cushing's disease

The treatment of Cushing's disease is very complex and represents a challenge for clinicians. Transphenoidal surgical excision of adrenocorticotropic hormone (ACTH)-secreting pituitary adenoma remains the treatment of choice but, unfortunately, the rate of cure at long-term follow-up is suboptimal and recurrences are high, even in the hands of skilled neurosurgeons. Other treatment options, such as bilateral adrenalectomy and pituitary radiotherapy, are currently in use but no treatment has proven fully satisfactory during the lengthy progress of this chronic and devastating disease. Nelson's syndrome and hypopituitarism are of particular concern as affected patients need lifelong hormone-replacement therapy and have notably increased mortality. Although medical treatment represents a second-line treatment option in patients with Cushing's disease, so far pharmacological therapy has been considered a transient and palliative treatment. Many drugs have been employed: they may act at the hypothalamic-pituitary level, decreasing ACTH secretion; at the adrenal level, inhibiting cortisol synthesis (steroidogenesis inhibitors); or at the peripheral level by competing with cortisol (glucocorticoid receptor antagonists). Recently, there has been renewed interest in the medical therapy of Cushing's disease and pituitary-directed drugs include old compounds commercially available for other diseases, such as cabergoline, and new promising compounds, such as pasireotide (SOM230) or retinoic acid. This review focuses on the tumor-directed pharmacological approaches for the management of Cushing's disease based on the recent identification of possibile targets at a pituitary level.

[New medical treatments in pituitary adenomas]

Currently, the role of dopaminergic and somatostatinergic agonists in the treatment of pituitary adenomas is quite well established. Nevertheless, a clearer understanding of the expression of dopaminergic and somatostatinergic receptors at the cellular level of pituitary adenomas as well as the development of newer analogues compounds may drastically change current therapeutic modalities. In particular, the emphasis on the co-expression of different receptors types or subtypes in adenomatous cells highlights functional interactions between receptors leading to an increase in their activity. Newer molecules are also in the process of development : new somatostatin analogues with more universal binding properties to different receptors subtypes, as well as chimeric molecules capable of binding to somatostatinergic and dopaminergic receptors. In the midst of GH-secreting pituitary adenomas, a positive correlation exists between the expression of Sst2 mRNA and the inhibition of GH release by somatostatin analogues. The involvement of Sst5 subtype in adenomas resistant to preferential Sst2 agonists has recently been proved. Another recently developed compound has a more universal Sst binding profile. This compound, named SOM-230, has a 25, 5 and 40 times higher binding affinity to Sst1, Sst3 and Sst5 receptors respectively, and 2,5 times lower affinity to Sst2, when compared to octreotide. SOM-230 could therefore allow for much more effective methods in treating patients suffering from acromegaly. Besides, the use of a chimeric molecule presenting a binding affinity to both Sst2 and D2 subtypes (BIM-23A287) inhibits the secretion of GH in ways similar to the Sst2 or D2 agonists used alone or concurrently but however in a concentration 50 times lower than that of the latter. The discovery of Sst5 and D2 subtypes at the level of corticotropic adenomas reveals newer therapeutic perspectives with promising preliminary results with the use of SOM-230 ; these finding lead to a rise in interest in cabergoline. In the midst of non-functioning pituitary adenomas, the expression of Sst2, Sst3 and D2 receptors will perhaps allow the use of combined therapies associating the new somatostatin analogues to the dopaminergic agonists or even use dopastatin (BIM-23A760, chimeric molecule Sst2-Sst5-D2). The preliminary results obtained in vitro with this molecule are actually encouraging since they show a dose dependent inhibition of the cellular replication mechanisms in 60 % of the cases. Finally, concerning prolactinomas the discovery of Sst5 receptors lead to consider the use of somatostatinergic agonists specific to the Sst5 receptor, SOM-230 in particular. Nevertheless, it seems that adenomas resistant to dopaminergic agonist due to a lack of expression of D2 receptor fail to express Sst5 receptors as well. On the other hand, dopastatin appears to be more efficient than cabergoline in the management of this type of adenomas. Therefore, the growing awareness concerning the mechanisms involved in the control of pituitary secretions as well as cellular proliferation will perhaps allow physicians to treat the pathology of pituitary adenomas, macroadenomas in particular, using solely pharmacological means instead of invasive surgical procedures and/or radiotherapy.

Pituitary-targeted medical therapy of Cushing's disease

BACKGROUND

The goals of ideal medical therapy for Cushing's disease should be to target the aetiology of the disorder, as is the case for surgery, which is the current 'gold standard' treatment. However, no effective drug that directly and reliably targets the adrenocorticotropin-secreting pituitary adenoma has yet been found.

OBJECTIVE

To summarise pituitary-targeted medical treatment of Cushing's disease.

METHODS

Compounds with neuromodulatory properties and ligands of different nuclear hormone receptors involved in hypothalamo-pituitary regulation have been investigated.

RESULTS

The somatostatin analogue pasireotide and the dopamine agonist cabergoline, as well as their combination, show some therapeutic promise in the medical therapy of Cushing's disease. Other treatments such as retinoic acid analogues look promising and may be a possible option for further investigation. No other medical therapies seem to be reliably effective currently.

CONCLUSION

Since a percentage of patients treated with surgery are not cured, or improve and subsequently relapse, there is an urgent need for effective medical therapies for this disorder. At present, only cabergoline and pasireotide are under active investigation.

Advances in medical treatment of Cushing's disease

It is well known that transphenoidal surgery is the first line of treatment for Cushing's disease (CD). In case of recurrence, pituitary irradiation or adrenalectomy are usually performed; however, the morbidity due to these procedures is not negligible. For this reason, there is still a strong need for medical therapy, although there are only a few controlled data on this field. A variety of compounds are invaluable complementary tools in the management of this serious condition for which no treatment has yet been proven fully satisfactory. Pharmacological treatment could be employed by using neuromodulatory drugs (i.e., serotonin antagonists, dopamine, and GABA agonists) active only in a few cases of hypothalamic-pituitary-dependent CD. New approaches at the pituitary tumor level involve the potential use of other compounds (e.g., PPAR-γ agonists and retinoic acid). Exciting news in treating CD includes the recent availability of new multiligand somatostatin analogues. This review focuses on the new potential pharmacologic approaches for the management of CD based on the recent identification of possible targets and/or pathogenetic mechanisms.

Control of pituitary adenoma cell proliferation by somatostatin analogs, dopamine agonists and novel chimeric compounds

The antisecretory effects of somatostatin (SRIH) and its analogs are widely recognized and provide the basis for treatment of hormonal hypersecretion in patients with pituitary adenomas, especially in the settings of acromegaly. Dopamine (DA) agonists have also been used for medical treatment of prolactin and/or GH hypersecretion, and recent evidence points to an even greater antisecretory effect for a chimeric molecule, having high affinity for both SRIH and DA receptors. Evidence for an antiproliferative effect of these compounds has also been provided. This review focuses on the antiproliferative effects of SRIH and its analogs, of DA and chimeric compounds on pituitary adenomas, and on the clinical consequences on tumor volume of pharmacological treatment of pituitary adenomas with these drugs.