Cabergoline treatment in acromegaly: pros

Standards of care for medical management of acromegaly in pituitary tumor centers of excellence (PTCOE)

PURPOSE

A series of consensus guidelines on medical treatment of acromegaly have been produced in the last two decades. However, little information is available on their application in clinical practice. Furthermore, international standards of acromegaly care have not been published. The aim of our study was to report current standards of care for medical therapy of acromegaly, using results collected through an audit performed to validate criteria for definition of Pituitary Tumor Centers of Excellence (PTCOE).

METHODS

Details of medical treatment approaches to acromegaly were voluntarily provided by nine renowned international centers that participated in this audit. For the period 2018-2020, we assessed overall number of acromegaly patients under medical treatment, distribution of patients on different treatment modalities, overall biochemical control rate with medical therapy, and specific control rates for different medical treatment options.

RESULTS

Median number of total patients and median number of new patients with acromegaly managed annually in the endocrinology units of the centers were 206 and 16.3, respectively. Median percentage of acromegaly patients on medical treatment was 48.9%. Among the patients on medical treatment, first-generation somatostatin receptor ligand (SRL) monotherapy was used with a median rate of 48.7%, followed by combination therapies with a median rate of 29.3%. Cabergoline monotherapy was used in 6.9% of patients. Pegvisomant monotherapy was used in 7 centers and pasireotide monotherapy in 5 centers, with median rates of 7.9% and 6.3%, respectively.

CONCLUSIONS

Current standards of care in PTCOEs include use of first-generation SRLs as the first medical option in about 50% of patients, as recommended by consensus guidelines. However, some patients are kept on this treatment despite inadequate control suggesting that cost-effectiveness, availability, patient preference, side effects, and therapeutic inertia may play a possible role also in PTCOE. Moreover, at odds with consensus guidelines, other monotherapies for acromegaly appear to have a marginal role as compared to combination therapies as extrapolated from PTCOE practice data. Presence of uncontrolled patients in each treatment category suggest that further optimization of medical therapy, as well as use of other therapeutic tools such as radiosurgery may be needed.

Effectiveness of combined first-line medical treatment in acromegaly with prolactin cosecretion

OBJECTIVE

The aim of this study is to compare the response to first-line medical treatment in treatment-naive acromegaly patients with pure growth hormone (GH)-secreting pituitary adenoma (GH-PA) and those with GH and prolactin cosecreting PA (GH&PRL-PA).

DESIGN

This is a retrospective multicentric study of acromegaly patients followed from 2003 to 2023 in 33 tertiary Spanish hospitals with at least 6 months of first-line medical treatment.

METHODS

Baseline characteristics, first-line medical treatment strategies, and outcomes were analyzed. We employed a multiple logistic regression full model to estimate the impact of some baseline characteristics on disease control after each treatment modality.

RESULTS

Of the 144 patients included, 72.9% had a GH-PA, and 27.1% had a GH&PRL-PA. Patients with GH&PRL-PA were younger (43.9 ± 15.0 vs 51.9 ± 12.7 years, P < .01) and harboring more frequently macroadenomas (89.7% vs 72.1%, P = .03). First-generation somatostatin receptor ligand (fgSRL) as monotherapy was given to 106 (73.6%) and a combination treatment with fgSRL and cabergoline in the remaining 38 (26.4%). Patients with GH&PRL-PA received more frequently a combination therapy (56.4% vs 15.2%, P < .01). After 6 months of treatment, in the group of patients under fgSRL as monotherapy, those patients with GH&PRL-PA had worse control compared to GH-PAs (29.4% vs 55.1%, P = .04). However, these differences in the rate of disease control between both groups disappeared when both received combination treatment with fgSRL and cabergoline.

CONCLUSION

In GH&PRL-PA, the biochemical control achieved with fgSRL as monotherapy is substantially worse than in patients harboring GH-PA, supporting the inclusion of cabergoline as first-line medical treatment in combination with fgSRLs in these subgroups of patients.

Medical treatment of functional pituitary adenomas, trials and tribulations

CONTEXT

Functioning pituitary adenomas (FPAs) include most frequently prolactinomas, somatotroph or corticotroph adenomas, while thyrotroph and gonadotroph adenomas are very rare. Despite their benign histological nature (aggressive tumors are rare and malignant ones exceptional), FPAs could cause significant morbidity and increased mortality due to complications associated with hormonal excess syndromes and/or mass effect leading to compression of adjacent structures. This mini review will focus on the increasing role of medical therapy in the multimodal treatment, which also includes transsphenoidal surgery (TSS) and radiotherapy.

EVIDENCE SYNTHESIS

Most patients with prolactinomas are treated only with medications, but surgery could be considered for some patients in a specialized pituitary center, if higher chances of cure. Dopamine agonists, especially cabergoline, are efficient in reducing tumor size and normalizing prolactin. TSS is the first-line treatment for all other FPAs, but most patients require complex adjuvant treatment, including a combination of therapeutic approaches. Medical therapy is the cornerstone of treatment in all patients after unsuccessful surgery or when surgery cannot be offered and includes somatostatin receptor ligands and dopamine agonists (almost all FPAs), growth hormone receptor antagonists (acromegaly), adrenal steroidogenesis inhibitors and glucocorticoid receptor blockers (Cushing's disease). Novel medical treatments, especially for acromegaly and Cushing's disease are under research.

CONCLUSIONS

An enlarged panel of effective drugs available with increased knowledge of predictive factors for response and/or adverse effects will enhance the possibility to offer a more individualized treatment. This would not only improve disease control and prognosis, but also quality of life.

Long-term efficacy and safety of subcutaneous pasireotide alone or in combination with cabergoline in Cushing's disease

Objective

This study evaluated short- and long-term efficacy and safety of the second-generation somatostatin receptor ligand pasireotide alone or in combination with dopamine agonist cabergoline in patients with Cushing's disease (CD).

Study design

This is an open-label, multicenter, non-comparative, Phase II study comprising 35-week core phase and an optional extension phase. All patients started with pasireotide, and cabergoline was added if cortisol remained elevated. Eligible patients had active CD, with or without prior surgery, were pasireotide naïve at screening or had discontinued pasireotide for reasons other than safety. Primary endpoint was proportion of patients with a mean urinary free cortisol (mUFC) level not exceeding the upper limit of normal (ULN) at week 35 with missing data imputed using last available post-baseline assessments.

Results

Of 68 patients enrolled, 26 (38.2%) received pasireotide monotherapy and 42 (61.8%) received pasireotide plus cabergoline during the core phase. Thirty-four patients (50.0%; 95% CI 37.6-62.4) achieved the primary endpoint, of whom 17 (50.0%) received pasireotide monotherapy and 17 (50.0%) received combination therapy. Proportion of patients with mUFC control remained stable during the extension phase up to week 99. Treatment with either mono or combination therapy provided sustained improvements in clinical symptoms of hypercortisolism up to week 99. Hyperglycemia and nausea (51.5% each), diarrhea (44.1%) and cholelithiasis (33.8%) were the most frequent adverse events.

Conclusion

Addition of cabergoline in patients with persistently elevated mUFC on maximum tolerated doses of pasireotide is an effective and well-tolerated long-term strategy for enhancing control of hypercortisolism in some CD patients.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT01915303, identifier NCT01915303.

A systematic literature review to evaluate extended dosing intervals in the pharmacological management of acromegaly

PURPOSE

This systematic literature review investigated whether extended dosing intervals (EDIs) of pharmacological acromegaly treatments reduce patient burden and costs compared with standard dosing, while maintaining effectiveness.

METHODS

MEDLINE/Embase/the Cochrane Library (2001-June 2021) and key congresses (2018-2021) were searched and identified systematic literature review bibliographies reviewed. Included publications reported on efficacy/effectiveness, safety and tolerability, health-related quality of life (HRQoL), and patient-reported and economic outcomes in longitudinal/cross-sectional studies in adults with acromegaly. Interventions included EDIs of pegvisomant, cabergoline, and somatostatin receptor ligands (SRLs): lanreotide autogel/depot (LAN), octreotide long-acting release (OCT), pasireotide long-acting release (PAS), and oral octreotide; no comparator was required.

RESULTS

In total, 35 publications reported on 27 studies: 3 pegvisomant monotherapy, 11 pegvisomant combination therapy with SRLs, 9 LAN, and 4 OCT; no studies reported on cabergoline, PAS, or oral octreotide at EDIs. Maintenance of normal insulin-like growth factor I (IGF-I) was observed in ≥ 70% of patients with LAN (1 study), OCT (1 study), and pegvisomant monotherapy (1 study). Achievement of normal IGF-I was observed in ≥ 70% of patients with LAN (3 studies) and pegvisomant in combination with SRLs (4 studies). Safety profiles were similar across EDI and standard regimens. Patients preferred and were satisfied with EDIs. HRQoL was maintained and cost savings were provided with EDIs versus standard regimens.

CONCLUSIONS

Clinical efficacy/effectiveness, safety, and HRQoL outcomes in adults with acromegaly were similar and costs lower with EDIs versus standard regimens. Physicians may consider acromegaly treatment at EDIs, especially for patients with good disease control.

Dissecting the in vitro efficacy of octreotide and cabergoline in GH- and GH/PRL-secreting pituitary tumors

CONTEXT

Cabergoline (CAB) is an off-label medical therapy for acromegaly, overshadowed by first-generation somatostatin receptor ligands, e.g. octreotide (OCT).

OBJECTIVE

Head-to-head comparison between OCT and CAB in inhibiting growth hormone (GH) secretion in primary cultures of GH- and GH/PRL-secreting tumors. To investigate the role of somatostatin (SST) and dopamine type 2 (D2R) receptor expression.

DESIGN

To evaluate the antisecretory effect of OCT and CAB, together with receptor mRNA expression, in 23 tumor cultures.

SETTING AND PATIENTS

Acromegaly patients referred to the Erasmus Medical Center (Rotterdam, The Netherlands).

INTERVENTIONS

72-hour OCT and CAB treatment (10 nM).

MAIN OUTCOME MEASURES

GH concentrations in cell culture media.

RESULTS

OCT showed a slightly higher efficacy compared with CAB (GH decrease -39.5% vs. -32.5%, p = 0.079). The effect of the two drugs was superimposable in GH/PRL co-secreting tumors (-42.1% vs. -44.8%), where SST1 and D2R had a higher expression compared to the pure GH-secreting ones (p = 0.020 and p = 0.026). OCT was more effective than CAB in 8/23 cultures, while CAB was more effective than OCT in 3/23 (CAB + group). In CAB + tumors, SST1 expression was higher compared to the other groups (p = 0.034). At ROC curve analysis, SST1 and D2R discriminated between GH and GH/PRL co-secretion (AUC 0.856, p = 0.013; AUC 0.822, p = 0.024). SST1 was the best predictor of CAB response (≥50% GH reduction, AUC 0.913, p = 0.006; 80% sensitivity, 94% specificity).

CONCLUSIONS

OCT is 5-10% more effective than CAB in vitro. SST1 mRNA expression can represent a reliable marker of GH/PRL co-secreting tumors showing a preferential response to CAB treatment.

Anastrozole as add-on therapy for cabergoline-resistant prolactin-secreting pituitary adenomas: real-life experience in male patients

INTRODUCTION

Prolactin-secreting adenoma (PRLoma) can present as large and invasive neoplasm, with increased markers of cellular proliferation. First-line approach is Dopamine Agonists (DAs) treatment; however, DA-resistance has been reported, especially in male patients. Estrogens induce lactotroph cell replication and PRL secretion: the use of anti-estrogen treatment in patients with PRLoma have been described in few cases. We reported our experience regarding treatment with the aromatase inhibitor anastrozole (ANA) as add-on therapy for male patients with DA resistant PRLoma.

MATERIALS AND METHODS

We describe four male patients (26, 38, 29 and 19 years old at diagnosis), with PRLoma (median diameter 26 mm, PRL 7730 μg/L). They were resistant to cabergoline (CAB, > 2 mg/week) in terms of PRL secretion and tumor size reduction. ANA 1 mg/day was added to the maximum tolerated dose of CAB for at least 1 year. Magnetic Resonance was performed at baseline, after 6 months of CAB + ANA combination and every 12 months afterward.

RESULTS

PRL levels decreased in all patients after CAB + ANA (mean - 70%, range - 44/- 97%), achieving a normalization of PRL levels in one case. Tumor size decreased in all cases (mean - 47%, range - 24.5/- 68%). No severe adverse effects have been reported, a moderate weight gain has been observed in two cases.

CONCLUSIONS

Addition of an aromatase inhibitor (ANA) to the dopamine agonist therapy improved the control of prolactin levels and induced tumour regression.

Patients with acromegaly might not be at higher risk for dopamine agonist-induced impulse control disorders than those with prolactinomas

OBJECTIVE

To evaluate the prevalence of impulse control disorders (ICD) and psychiatric symptoms in patients with acromegaly receiving dopamine agonists (DA) in comparison with those with prolactinoma, nonfunctioning pituitary adenomas (NFA), and healthy controls (HC).

DESIGN

Forty patients with acromegaly, 40 with prolactinoma, 38 with NFA, and 32 HCs were included. All patients and controls were evaluated using the revised version of the Minnesota Impulsive Disorders Interview (MIDI-R), Symptom Check List (SCL-90-R) questionnaire, Barratt Impulsiveness Scale (BIS-11), Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI).

RESULTS

We detected ICD associated with DAs in two patients with acromegaly (5%) and three patients (7.5%) with prolactinoma. All patients' symptoms resolved after discontinuation of the drug. While the mean DA dose was higher in patients with acromegaly than prolactinomas (p < 0.05), no difference was detected in terms of ICD prevalence between two groups (p > 0.05). SCL-90 depression and interpersonal sensitivity subscale positivity was higher in patients with NFA than HCs. Patients with prolactinoma had higher obsession and interpersonal sensitivity positivity and those with NFA had higher somatization, interpersonal sensitivity, and depression positivity as compared to patients with acromegaly (p < 0.05 for all).

CONCLUSIONS

Although DA dose was significantly higher in patients with acromegaly, there was no significant difference in the prevalence of DA-related ICD. The higher prevalence of positive screening in SCL-90 in patients with NFA in comparison to HCs supports the hypothesis that the presence of a pituitary adenoma per se might cause significant psychiatric symptoms.

Epidemiology, clinical manifestations and efficiency of different methods of treatment of acromegaly according to the United Russian Registry of Patients with Pituitary Tumors

BACKGROUND: The registry is the main source of information about patients with acromegaly for assessing the quality of medical care, effectiveness of treatment, determining the compliance of real clinical practice with existing standards and patient management protocols. AIMS: To evaluate epidemiological, demographic and clinical characteristics of acromegaly in Russian Federation and effectiveness of treatment modalities. MATERIALS AND METHODS: The object of the study was the database of the united Russian registry of patients with pituitary tumors with specific analysis of patients with acromegaly only. We analyzed the data of 4114 patients with acromegaly stored on the online system in February 2019. RESULTS: Based on the data 32% of patients had complete clinical and laboratory remission of acromegaly; the percentage of patients with no remission was 68%, among them 22.5% had significant improvements in clinical symptoms and a decrease in growth hormone (GH) and insulin-like growth factor-1 (IGF-1) without IGF-1 normalization. The average age of patients at the onset of the disease was 42.7 years and at diagnosis 45.8 years. The ratio of men to women was 1:2.6. In patients with acromegaly hypopituitarism was registered in 14.7% of cases and among them hypothyroidism (66%) and hypogonadism (52%) were registered more often. Among other complications the leading were diabetes mellitus (15.7%) and acromegalic arthropathy (15%). The proportion of patients receiving neurosurgical treatment increased from 35.7% to 49.6% in 20122019; the portion of patients undergoing radiation therapy decreased significantly from 17.7% in 2012 to 0.8% in 2019. Remission was achieved in 40.47% after neurosurgery and 28.95% after medical treatment as a first line therapy p0.01. The number of patients receiving medical treatment at the time of the study was 1209. Among them 51% of patients treated with long-acting lanreotide and 24% receiving long-acting octreotide achieved remission (p0.0001) CONCLUSIONS: The remission rate of acromegaly remains suboptimal despite increased surgical activity, which corresponds to global trends. Long-acting lanreotide was significantly superior versus long-acting octreotide in the rate of acromegaly remission, which does not correspond with clinical trials.

Treatment of Pituitary and Other Tumours with Cabergoline: New Mechanisms and Potential Broader Applications

Cabergoline is a dopamine agonist that has been used as the first-line treatment option for prolactin-secreting pituitary adenomas for several decades. It not only suppresses hormone production from these prolactinomas, but also causes tumour shrinkage. Recent studies revealed some novel mechanisms by which cabergoline suppresses tumour cell proliferation and induces cell death. In this article, we review the most recent findings in cabergoline studies, focusing on its anti-tumour function. These studies suggest the potential broader clinical use of cabergoline in the treatment of other tumours such as breast cancer, pancreatic neuroendocrine tumours, and lung cancer.

Bringing Cardiovascular Comorbidities in Acromegaly to an Update. How Should We Diagnose and Manage Them?

Patients with acromegaly frequently develop cardiovascular comorbidities, which significantly affect their morbidity and contribute to an increased all-cause mortality. In this regard, the most frequent complications that these patients may encounter include hypertension, cardiomyopathy, heart valve disease, arrhythmias, atherosclerosis, and coronary artery disease. The specific underlying mechanisms involved in the pathophysiology of these comorbidities are not always fully understood, but uncontrolled GH/IGF-I excess, age, prolonged disease duration, and coexistence of other cardio-vascular risk factors have been identified as significant influencing predisposing factors. It is important that clinicians bear in mind the potential development of cardiovascular comorbidities in acromegalic patients, in order to promptly tackle them, and avoid the progression of cardiac abnormalities. In many cases, this approach may be performed using straightforward screening tools, which will guide us for further diagnosis and management of cardiovascular complications. This article focuses on those cardiovascular comorbidities that are most frequently encountered in acromegalic patients, describes their pathophysiology, and suggests some recommendations for an early and optimal diagnosis, management and treatment.

Dopamine Agonists for Pituitary Adenomas

Dopamine agonists (DA) are well established as first-line therapy for prolactinomas. These tumors express high levels of dopamine 2 receptors (D2R), leading to the strong efficacy of DA in reducing tumor size and hormonal secretion. Other pituitary tumor subtypes express D2R to varying degrees, leading to an extensive body of research into potential off-label use of DA in non-prolactinoma pituitary tumors. Preclinical models of Cushing's disease, acromegaly, and nonfunctioning pituitary tumors (NFPT) demonstrate D2R expression in cell lines and cultured tumors as well as effectiveness of DA in reducing hormonal secretion in functioning tumors and arresting tumor proliferation. Clinical studies have shown some efficacy of DA in treatment of these tumors. In Cushing's disease, DA therapy results in normalization of urinary cortisol levels in approximately 25% of patients, but reported rates of tumor shrinkage are very low; in acromegaly, DA therapy leads to normalization of insulin-like growth factor I and tumor shrinkage in approximately one-third of patients, and improved responses when used in combination with somatostatin receptor ligands. Among patients with NFPT, pooled results show 30% experience reduction of tumor size and 58% show stabilization of disease. DA therapy appears to have some clinical benefit in patients with non-prolactinoma pituitary tumors, and may be an option for medical therapy in some clinical scenarios.

Cabergoline in acromegaly

Acromegaly, a rare disease due to growth hormone (GH) hypersecretion by a pituitary adenoma, is associated with severe comorbidity and premature death if not adequately treated. The usual first-line treatment is surgery. Various drugs, including somatostatin receptor ligands, dopamine agonists and GH receptor antagonists, are now available for use if surgery fails to suppress GH/IGF-I hypersecretion. Cabergoline, now the preferred dopamine agonist for treating hyperprolactinemia, is also used off-label for treating acromegaly. Cabergoline monotherapy is reported to normalize IGF-I levels in more than one-third of patients with acromegaly. When a somatostatin receptor ligand proves ineffective, cabergoline add-on therapy normalizes the IGF-I level in 40-50% of patients. Finally, when combined with the GH receptor antagonist pegvisomant in patients with mild uncontrolled disease, cabergoline helps to achieve normal IGF-I levels while avoiding the need for high-dose pegvisomant. Cabergoline is also inexpensive and well tolerated; in particular, it does not appear to promote heart valve disease.

Cardiovascular comorbidities in acromegaly: an update on their diagnosis and management

Comorbidities related to the cardiovascular system are one of the most prevalent in patients with acromegaly, and contribute to an increased risk of morbidity and all-cause mortality. Specifically, hypertension, cardiomyopathy, heart valve disease, arrhythmias, atherosclerosis, coronary artery disease, and cardiac dysfunction may be frequent findings. Although the underlying physiopathology for each comorbidity may not be fully elucidated, uncontrolled growth hormone/insulin-like growth factor 1 excess, age, prolonged disease duration, and coexistence of other cardio-vascular risk factors are significant influencing variables. A simple diagnostic approach to screen for the presence of these comorbidities may allow prompt treatment and arrest the progression of cardiac abnormalities. In this article, we revise the most prevalent cardiovascular comorbidities and their pathophysiology in acromegalic patients, and we address some recommendations for their prompt diagnosis, management and treatment. Strengths and pitfalls of different diagnostic techniques that are currently being used and how different treatments can affect these complications will be further discussed.

Somatostatin and dopamine receptor regulation of pituitary somatotroph adenomas

Somatostatin and dopamine receptors are expressed in normal and tumoral somatotroph cells. Upon receptor stimulation, somatostatin and the somatostatin receptor ligands octreotide, lanreotide, and pasireotide, and to a lesser extent, dopamine and the dopamine analogs bromocriptine and cabergoline, suppress growth hormone (GH) secretion from a GH-secreting pituitary somatotroph adenoma. Somatostatin and dopamine receptors are G_αi-protein coupled that inhibit adenylate cyclase activity and cAMP production and reduce intracellular calcium concentration and calcium flux oscillations. Although their main action on somatotroph cells is acute inhibition of GH secretion, they also may inhibit GH production and possibly somatotroph proliferation. These receptors have been reported to create complexes that exhibit functions distinct from that of receptor monomers. Somatostatin suppression of GH is mediated mainly by somatostatin receptor subtype 2 and to a lesser extent by SST5. Human somatostatin receptor subtype 5 has also been shown to harbor mutations associated with GH levels, somatotroph tumor behavior, and somatostatin receptor ligand (SRL) responsiveness. Reviewing current knowledge of somatostatin and dopamine receptor expression and signaling in normal and tumoral somatotroph cells offers insights into mechanisms underlying SRL and dopamine agonist effectiveness in patients with acromegaly.

Somatostatin analogs, cabergoline and pegvisomant: comparing the efficacy of medical treatment for acromegaly

Therapies for acromegaly aim at normalizing hormonal excess and controlling tumor growth . Therapeutic approaches are surgery, pharmacotherapy and radiotherapy. Area covered: This review focuses on the role of medical therapy of acromegaly, comparing the efficacy of somatostatin analogues (SSA), dopamine-agonists (DA) and pegvisomant (PEG), the three available drug classes for treating acromegaly. To clarify the difference in response rates reported in the literature for these therapies, we performed a search for original articles published in PubMed. SSA represent the first-line approach to medical treatment. This therapy is effective in controlling acromegaly in about 40% of patients, however there are great differences in the reported hormonal efficacy of SSA in the different series. In patients partially resistant to SSA, cabergoline can be added when hormonal levels are close to normalization, resulting effective in control IGF-I levels in 43% of patients. In patients with higher hormonal levels PEG is indicated, normalizing IGF-I levels in 79.8% and 80.6% of cases when used in monotherapy or in combination with SSA. Pasireotide, the newly developed SSA multi-ligand receptor, represents a new option in SSA resistant patients. Expert commentary: Medical therapy represents an important therapeutic option resulting safe and effective in controlling acromegaly in a high percentage of patients. The best treatment should be individually tailored for each patient, taking into account sex, age, comorbidities, tumor characteristics and hormonal levels.

New medical therapies of acromegaly

Acromegaly is a rare disease associated with significant morbidity and increased mortality. Treatment of acromegaly aims at controlling growth hormone hypersecretion, improving patients' symptoms and comorbidities and normalizing mortality. The therapeutic options for acromegaly include surgery, medical therapies and radiotherapy. However, despite all these treatment options, approximately one-half of patients are not adequately controlled. Progress in molecular research has made possible to develop new therapeutic strategies to improve control of acromegaly. This article will review the new medical approaches to acromegaly which consist in evolution of traditional therapeutic protocols and development of new molecules with different profiles of activity.

Current and Emerging Aspects of Diabetes Mellitus in Acromegaly

Diabetes mellitus is a frequent complication of acromegaly, a disease characterized by chronic hypersecretion of growth hormone (GH) by a pituitary adenoma. Diabetes occurs commonly but not only as a consequence of an insulin-resistant state induced by GH excess. The development of diabetes in patients with acromegaly is clinically relevant, since such a complication is thought to increase the already elevated cardiovascular morbidity and mortality risk of the disease. Emerging data suggest that a specific cardiomyopathy can be identified in acromegaly patients with diabetes. Moreover, the presence of diabetes may also influence therapeutic decision making in acromegaly, since traditional and newly developed drugs used in this clinical setting may impact glucose metabolism regardless of control of GH hypersecretion.

Current and future medical treatments for patients with acromegaly

INTRODUCTION

Acromegaly is a relatively rare condition of growth hormone (GH) excess associated with significant morbidity and, when left untreated, high mortality. Therapy for acromegaly is targeted at decreasing GH and insulin-like growth hormone 1 levels, ameliorating patients' symptoms and decreasing any local compressive effects of the pituitary adenoma. The therapeutic options for acromegaly include surgery, medical therapies (such as dopamine agonists, somatostatin receptor ligands and the GH receptor antagonist pegvisomant) and radiotherapy. However, despite all these treatments option, approximately 50% of patients are not adequately controlled.

AREAS COVERED

In this paper, the authors discuss: 1) efficacy and safety of current medical therapy 2) the efficacy and safety of the new multireceptor-targeted somatostatin ligand pasireotide 3) medical treatments currently under clinical investigation (oral octreotide, ITF2984, ATL1103), and 4) preliminary data on the use of new injectable and transdermal/transmucosal formulations of octreotide.

EXPERT OPINION

This expert opinion supports the need for new therapeutic agents and modalities for patients with acromegaly.

Long-term treatment with pegvisomant for acromegaly: a 10-year experience

BACKGROUND

Efficacy of the GH-receptor antagonist pegvisomant (PEG) has differed between preclinical and observational studies mainly due to dose adjustment and IGF-I normalization criteria. An escape phenomenon has also been described, but its definition and underlying causes have not been fully established.

OBJECTIVE

To re-evaluate the outcomes of long-term PEG in a series of previously published patients and analyse the escape phenomenon.

METHODS

We reviewed all patients with acromegaly resistant to SSA in whom PEG was started as monotherapy, who had been included in a previous publication. We prospectively evaluated 64 (56·3% women) from six tertiary care referral hospitals in Spain, for whom data as of June 2014 were available. Escape to PEG was defined as confirmed loss of biochemical control (IGF-I >1·2xULN), after at least 6 months of previous control with a stable dose of PEG.

RESULTS

Patients were followed up for 13·0 (5·9-34·8) years since diagnosis, and 9·0 (4·1-10·4) years since the first administration of PEG. Fifty-one (89·5%) patients had an adequate IGF-I control at the last follow-up visit, 9 of them without treatment. Tumour growth was reported in 6 of 64 cases (9·4%), none of whom had received prior radiotherapy (P = 0·011). Seven patients died during follow-up. We found 16 escapes in 10 patients (15·6%). We identified potential underlying causes in 9 cases (tumour regrowth, previous treatment modifications, concomitant menopause and change in testosterone administration). The reason was unknown in 7 escapes, which occurred in 6 patients (9·4%). All patients, except one, achieved subsequent biochemical control after treatment adjustment.

CONCLUSIONS

We reassure the efficacy and safety of long-term PEG. An escape phenomenon may occur, but it can be overcome by adjusting therapy.

Growth hormone tumor histological subtypes predict response to surgical and medical therapy

Growth hormone (GH) pituitary tumors are associated with significant morbidity and mortality. Current treatments, including surgery and medical therapy with somatostatin analogs (SSA), dopamine agonists and/or a GH receptor antagonist, result in disease remission in approximately half of patients. Predictors of GH tumor response to different therapies have been incompletely defined based on histologic subtype, particularly densely (DG) versus sparsely (SG) granulated adenomas. The aim of this study was to examine our own institutional experience with GH adenomas and correlate how subtype related to clinical parameters as well as response to surgery and medical therapies. A retrospective chart review of 101 acromegalic patients operated by a single neurosurgeon was performed. Clinical data were correlated with histologic subtype and disease control, as defined by IGF-1 levels, and random growth hormone levels in response to surgery and/or medical therapies. SG tumors, compared to DG, occurred in younger patients (p = 0.0010), were 3-fold larger (p = 0.0030) but showed no differences in tumor-invasion characteristics (p = 0.12). DG tumors had a higher rate of remission in response to surgery compared to SG, 65.7 vs. 14.3 % (p < 0.0001), as well as to medical therapy with SSAs (68.8 % for DG vs. 28.6 % for SG tumors; p = 0.028). SG tumors not controlled with SSAs consistently responded to a switch to, or addition of, a GH receptor antagonist. Histological GH tumor subtyping implicates a different clinical phenotype and biologic behavior, and provides prognostic significance for surgical success and response to medical therapies.

Bone turnover, bone mineral density, and fracture risk in acromegaly: a meta-analysis

CONTEXT

GH excess causes an increase in bone turnover, but the consequences in terms of skeletal fragility have long been uncertain due to the heterogeneity of studies dealing with this topic.

OBJECTIVE

We conducted a meta-analysis of studies examining the effects of acromegaly on bone turnover, bone mineral density (BMD), and fractures. Furthermore, we evaluated the effects of sex, gonadal status, and activity of disease on skeletal end-points in acromegaly.

DATA SOURCES

We conducted MEDLINE and EMBASE systematic searches up to December 31, 2013.

STUDY ELIGIBILITY CRITERIA

Studies conducted in patients with acromegaly and reporting at least one determinant of skeletal fragility.

DATA EXTRACTION AND ANALYSIS

Study design, patient characteristics, interventions, and outcomes were independently extracted by two authors. We calculated the standardized mean difference (SMD) of bone turnover and BMD differences, whereas fractures were presented as relative frequencies in acromegaly and odds ratios between patients and controls.

RESULTS

Forty-one studies fulfilled eligibility criteria and were therefore selected for data extraction and analysis. A total of 1935 patients were included (eight to 206 per study). Acromegaly patients had higher bone formation (SMD, 1.49; 95% confidence interval [CI], 0.97-2.01; P < .0001) and bone resorption (SMD, 1.57; 95% CI, 1.03-2.10; P < .0001) as compared to control subjects, without significant differences in lumbar spine BMD. BMD at the femoral neck tended to be higher in acromegaly patients vs control subjects (SMD, 0.67; 95% CI, 0.07-1.27; P = .03). Patients with acromegaly had high frequency of vertebral fractures (odds ratio, 8.26; 95% CI, 2.91-23.39; P < .0001), in close relationship with male gender, hypogonadism, and active acromegaly.

LIMITATIONS

LIMITATIONS included heterogeneous study protocols with possible variability in the assessment of skeletal end-points.

CONCLUSIONS

Skeletal fragility is an emerging complication of acromegaly.

Second Attempt of Cabergoline Withdrawal in Patients with Prolactinomas after a Failed First Attempt: Is it Worthwhile?

Successful discontinuation of cabergoline (CAB) treatment has been reported in 31-75% of prolactinomas patients treated for at least 2 years. In contrast, it is not well established whether CAB therapy can be successfully withdrawn after a failed first attempt. This prospective open trial was designed to address this topic and to try to identify possible predictor factors. Among 180 patients with prolactinomas on CAB therapy, the authors selected those who fulfilled very strict criteria, particularly additional CAB therapy for at least 2 years, normalization of serum prolactin (PRL) levels following CAB restart, no tumor remnant >10 mm, no previous pituitary radiotherapy or surgery; and current CAB dose ≤1.0 mg/week. Recurrence was defined as an increase of PRL levels above the upper limit of normal. A total of 34 patients (70.6% female) treated with CAB for 24-30 months were recruited. Ten patients (29.4%) remained without evidence of recurrence after 24-26 months of follow-up. Twenty-four patients (70.6%) recurred within 15 months (75% within 12 months) after drug withdrawal and ~80% were restarted CAB. Median time to recurrence was 10.5 months (range, 3-15). Despite overlapping values, non-recurring patients had significantly lower mean PRL levels before withdrawal. Moreover, the recurrence rate was lower in subjects without visible tumor on pituitary magnetic resonance imaging (MRI) than in those with small remnant tumor (60 vs. 79%), though the difference was not statistically significant (P = 0.20). No other characteristic could be identified as a predictor of successful CAB discontinuation. In conclusion, a second attempt of CAB withdrawal after two additional years of therapy may be successful, particularly in patients with lower PRL levels and no visible tumor on pituitary MRI. Close monitoring of PRL level is mandatory, especially within the first year after withdrawal, where most recurrences are detected.

Growth hormone deficiency in treated acromegaly

Growth hormone deficiency (GHD) of the adult is characterized by reduced quality of life (QoL) and physical fitness, skeletal fragility, and increased weight and cardiovascular risk. Hypopituitarism may develop in patients after definitive treatment of acromegaly, but an exact prevalence of GHD in this population is still uncertain owing to limited awareness and the scarce and conflicting data available on this topic. Because acromegaly and GHD may yield adverse consequences on similar target systems, the final outcomes of some complications of acromegaly may be further affected by the occurrence of GHD. However, it is still largely unknown whether patients with post-acromegaly GHD may benefit from GH replacement. We review the diagnostic, clinical, and therapeutic aspects of GHD in adult patients treated for acromegaly.

Surgical treatment of microprolactinomas: pros

Medical therapy with dopaminergic agonists (DAs) has been used for several decades for the treatment of both micro- and macroprolactinomas, without much differentiation between the two conditions. While most cases respond well to DAs in terms of prolactin normalization and control of tumor growth, DAs are often needed for many years, or even for lifetime. Concerns have been raised recently about the possible side effects of long-term use of these medications on the anatomy and function of the heart valves. While macroprolactinomas are rarely surgically curable, pituitary surgery in expert hands is a safe and effective method to permanently cure microprolactinomas, with long-term cure rates around 70 %. In this article, I will review the data on safety of DAs an on the effectiveness and safety of surgery, and I will make an argument that surgery should be offered as a possible therapy to microprolactinoma patients, provided that an experienced pituitary neurosurgeon is available.