Remission of acromegaly following long-term therapy with cabergoline: report of two cases

Remission of acromegaly after treatment withdrawal in patients controlled by cabergoline alone or in combination with octreotide: results from a multicenter study

PURPOSE

Remission of acromegaly has been reported after somatostatin analogs withdrawal, but not after withdrawal of combination therapy with cabergoline, and only in case reports of patients controlled by cabergoline alone.

METHODS

To establish the remission rates (normal IGF-1 for age/sex: IGF-1 ≤ 1.00 xULN) after withdrawal of combined treatment with octreotide LAR and cabergoline and of cabergoline alone, we prospectively studied 16 patients with acromegaly controlled by those treatments in the preceding 2 years as part of a larger study on remission of acromegaly after withdrawal of different medical treatments.

RESULTS

Among 97 patients with controlled acromegaly included in the entire study, only 16 patients had been on combination therapy (n = 12) or cabergoline alone (n = 4). At 8 weeks after treatment withdrawal, three patients (19%) were in remission (short-term remission). At 60 weeks (long-term remission), IGF-1 levels were still in the normal range in two patients (12.5%) and remained normal up to 108 weeks after treatment withdrawal (last visit). One patient had been treated with cabergoline alone and another one with combination of octreotide and cabergoline before treatment withdrawal.

CONCLUSION

Remission of acromegaly after treatment withdrawal seems to be uncommon in patients controlled by cabergoline, either as monotherapy or in combination with octreotide. In the future, larger studies and/or meta-analysis will be necessary to accurately establish the remission rates of acromegaly after withdrawal of cabergoline with or without somatostatin analogs.

Genetic Predictors of Response to Different Medical Therapies in Acromegaly

In the era of predictive medicine, management of diseases is evolving into a more personal and individualized approach, as more data are available regarding clinical, biochemical, radiological, molecular, histopathological, and genetic aspects. In the particular setting of acromegaly, which is a rare, chronic, debilitating, and disfiguring disease, an optimized approach deems even more necessary, especially because of an associated increased morbidity and mortality, the impact on patients' quality of life, and the increased cost of frequently necessary life-long treatments. In this paper, we review the available studies that address potential genetic influences on acromegaly, their role in the outcome, and response to treatments, as well as their contribution to the risk of developing side effects. We focus mainly on pharmacogenetic factors involved during treatment with dopamine agonists, somatostatin analogs, and pegvisomant. Specifically, mutations in dopamine receptors, somatostatin receptors, growth hormone receptors, and metabolic pathways involved in growth hormone action; polymorphisms in the insulin-like growth factor and the insulin-like growth factor binding proteins; and polymorphisms in other genes that may determine differences in the frequency of developing adverse events.

Cabergoline treatment in acromegaly: pros

Cabergoline is an ergot-derived dopamine D2 receptor agonist which may be effective for the medical management of acromegaly. Its efficacy in reducing growth hormone and IGF-I levels, as well as its antiproliferative and pro-apoptotic effects on pituitary tumor cells, has been observed in several studies. Cabergoline may be used alone or as an add-on therapy to patients who are partially resistant to somatostatin analogs (SSA), or who do not achieve complete control with maximum doses of pegvisomant (PEG). Additionally, the convenience of its oral administration, allowing better compliance, and its lower economic cost, in comparison with SSA and PEG, favor cabergoline as an attractive option for acromegalic patients, who frequently require long-life medical treatment to achieve disease control. The few adverse events observed with prolonged DA therapy, mainly regarding cardiac valve disease, are not frequent at the doses generally used in acromegaly.

Acromegalic patients lost to follow-up: a pilot study

Approximately 50 % of all acromegalic patients will require lifelong medical treatment to normalize mortality rates and reduce morbidity. Thus, adherence to therapy is essential to achieve treatment goals. To date, no study has evaluated the frequency and reasons for loss to follow-up in the acromegalic population. The current study aimed at evaluating the frequency of acromegalic patient loss to follow-up in three reference centers and the reasons responsible for their low compliance with treatment. All of the files for the acromegalic patients in the three centers were reviewed. Those patients, who had not followed up with the hospital for more than a year, were contacted via phone and/or mail and invited to participate. Patients who agreed to participate were interviewed, and blood samples were collected. A total of 239 files were reviewed; from these 42 patients (17.6 %) were identified who were lost to follow-up. It was possible to contact 27 of these patients, 10 of whom did not attend the appointments for more than one time and 17 of whom agreed to participate in the study. Fifteen of these 17 patients had active disease (88.2 %), and all of the patients restarted treatment in the original centers. The main reason for loss to follow-up was an absence of symptoms. High-quality follow-up is important in acromegaly to successfully achieve the aims of the treatment. An active search for patients may allow the resumption of treatment in a significant proportion of these cases, contributing to reduced morbidity and mortality in this patient population.

Pegvisomant and cabergoline combination therapy in acromegaly

Combination with cabergoline may offer additional benefits to acromegalic patients on pegvisomant monotherapy. We evaluated the safety and efficacy profile of this combination and investigated the determinants of response. An observational, retrospective, cross-sectional study. Fourteen acromegalic patients (9 females), who were partially resistant to somatostatin analogs and on pegvisomant monotherapy. Cabergoline was added because of the presence of persistent mildly increased IGF-I. The mean follow-up time was 18.3 ± 10.4 months. The efficacy and safety profile was assessed. The influence of clinical and biochemical characteristics on treatment efficacy was studied. IGF-I levels returned to normal in 4 patients (28%) at the end of the study. In addition, some decline in IGF-I levels was observed in a further 5 patients. The % IGF-I decreased from 158 ± 64% to 124 ± 44% (p = 0.001). The average change in IGF-I was -18 ± 27% (range -67 to +24%). Lower baseline IGF-I (p = 0.007), female gender (p = 0.013), lower body weight (p = 0.031), and higher prolactin (PRL) levels (p = 0.007) were associated with a better response to combination therapy. There were no significant severe adverse events. Significant tumour shrinkage was observed in 1 patient. Combination therapy with pegvisomant and cabergoline could provide better control of IGF-I in some patients with acromegaly. Baseline IGF-I levels, female gender, body weight, and PRL levels affect the response to this combination therapy.