The Effect of the Exon-3-Deleted Growth Hormone Receptor on Pegvisomant-Treated Acromegaly: A Systematic Review and Meta-Analysis

Abstract

Background: The common exon 3 deletion polymorphism of the growth hormone receptor (d3-GHR) is associated with disease severity in acromegaly patients. The GHR antagonist pegvisomant (PEGV) is highly effective in treating severe acromegaly. Response to PEGV treatment seems to be influenced by d3-GHR and appears to be more responsive to PEGV, although available results remain conflicting.

Objective: To assess the influence of d3-GHR on the responsiveness of acromegaly patients to PEGV by compiling the evidence derived from the largest available studies.

Design: A systematic review of the literature identified three published studies and one conference abstract. Acromegaly patients (n = 324, 49.7% d3-GHR carriers) were treated with either PEGV monotherapy or PEGV combined with long-acting somatostatin analogues and/or cabergoline. A meta-analysis of raw data from these studies was performed.

Results: No significant effect of the d3-GHR was observed while bringing insulin-like growth factor I (IGF-I) levels below the upper limit of normal with PEGV, which was defined as the lowest IGF-I level during PEGV treatment (mean difference: -2.3%; 95% CI: -6.5 to 1.8, p = 0.270). The PEGV dose required to achieve the lowest IGF-I levels was also not significantly influenced by individuals carrying d3-GHR (mean difference: 4.1 mg weekly; 95% CI: -5.1 to 13.2, p = 0.385). For both outcomes, separate analysis of PEGV monotherapy and combination treatment gave similar results.

Conclusion: Our findings suggest that the d3-GHR polymorphism has no effect on biochemical disease control in acromegaly, as it is not of added value for either the prediction of PEGV responsiveness or the determination of the required PEGV dose.

Keywords: Acromegaly; Deletion of exon 3; Growth hormone receptor; Meta-analysis; Pegvisomant; Polymorphism.

Fig. 1

Flow diagram of the study selection and exclusion stages.

Fig. 2

Forest plot of meta-analysis: effect of d3-GHR on IGF-I during PEGV. The summary effect of d3-GHR genotype with respect to fl/fl-GHR on the lowest IGF-I level ULN during PEGV treatment in patients treated with PEGV alone or in combination with LA-SSA and/or CAB (n = 43) has a mean difference of −2.3% relative to the ULN of IGF-I (95% CI: −6.5 to 1.8, p = 0.270). GHR = Growth hormone receptor; fl = full-length; d3 = deletion of exon 3; IGF-I = insulin-like growth factor I; ULN = upper limit of normal; PEGV = pegvisomant; LA-SSA = long-acting somatostatin analogues; CAB = cabergoline; CI = confidence interval.

Fig. 3

Forest plot of meta-analysis: effect of d3-GHR on the required PEGV dose. The summary effect of d3-GHR genotype with respect to fl/fl-GHR on the required PEGV dose needed to achieve normalization of IGF-I levels in patients treated with PEGV alone or in combination with LA-SSA and/or CAB (n = 43) has a mean difference of 4.06 mg weekly (95% CI: −5.1 to 13.2, p = 0.385). GHR = Growth hormone receptor; fl = full-length; d3 = deletion of exon 3; IGF-I = insulin-like growth factor I; ULN = upper limit of normal; PEGV = pegvisomant; LA-SSA = long-acting somatostatin analogues; CAB = cabergoline; CI = confidence interval.