Addition of Cabergoline Lowers IGF-I in Acromegaly after Failure of Octreotide-LAR Monotherapy

Presentation Number: SUN 452
Date of Presentation: April 2nd, 2017

Arthur Disegna, Armindo Jreige Jr., Rhenan Reis, Vitoria Espindola Leite Borges, Andre Metzker Ferro, Wesley Flavio Lima Jr. and Luciana Ansaneli Naves*
University of Brasilia, Brasilia, Brazil

Abstract

IGF-I is a stable, reliable and accessible parameter for evaluation of the control of Acromegaly. Somatostatin analogues as dopamine agonists may be used for secretory control and, in combination, appear to have an additive effect on lowering serum GH and IGF-I. However, the long-term effects of the combined therapy after failure of the somatostatin analogs monotherapy have never been demonstrated before. A retrospective, non-randomized study was made from a sample of 21 acromegalic patients in follow up between 2000 and 2016. Statistical analysis for categorical data were made with the Chi-square or the Fisher exact test when appropriate, comparisons of IGF values between groups or therapy modalities were made with the Student’s t-test and linear correlations were searched with the Pearson’s correlation test. Patients were treated for 50 ± 38 months with Octreotide-LAR (OCT) alone, causing the IGF-I levels to fall from 270 ± 76 at the time of diagnosis, to 173 ± 42 (p <0.0001) (values expressed as percentage of the upper limit of normal variation – ULNR – for each patient’s age group). After combination with cabergoline (CBG), levels further decreased to 140 ± 51% (p <0.01) and 7 patients (33%) achieved the therapeutic target for IGF-I. The association period lasted for 78 ± 36 months at doses of 2.2 ± 0.8 mg. The dose of CBG, basal levels of GH, IGF-I and prolactin and lesion volume were not shown to have any statistical correlation with the CBG response. However, patients who eventually normalized IGF-I levels have also shown a better partial response to OCT monotherapy (p<0.05). Patients with IGF-I below 220% of ULNV at diagnosis were more likely to achieve normalization (p <0.05). However, no overall relationship was shown between IGF-I levels at diagnosis or during monotherapy and proportional reduction in IGF-I levels after introduction of CBG. Furthermore, the short-term fall in IGF-I given by the first IGF-I result during the combined therapy accurately represented the long term follow up of IGF-I results from these patients, including those who did not meet the therapeutic target (P<0,001). No secretory relapse was observed during the follow up. These results are in accordance with past studies, which reported the benefits of association in a shorter term. Our study has shown that CBG addition is effective on reducing IGF-I levels of patients refractory to OCT therapy on the long term.

 

Nothing to Disclose: AD, AJ Jr., RR, VELB, AMF, WFL Jr., LAN