Endocrine Abstracts

Introduction: Pegvisomant (PEGV) has an efficacy of >90% to control insulin-like growth factor (IGF-1), however in everyday practice a limited efficacy of 63% was reported.

Aim: To assess efficacy in the largest single center cohort of acromegalics using PEGV.

Methods: A 112 subjects (65 male) were not controlled with high-dose somatostatin analogues (LA-SRIF) for at least 6 months. To control acromegaly, 109 subjects added PEGV and three used PEGV alone. IGF-1 and GH levels (start, lowest and last values) were retrospectively re-assessed in a single run. IGF-1 was measured by the Immulite2000 and GH by the IDS-iSYS immuno-assay, to assess GH without interference of PEGV. Results are expressed as median (interquartile range). At baseline 80% of the subjects (age 47.3 years (38.4–59.0)) had a macro-adenoma.

Results: Duration of PEGV treatment was 4.0 years (1.9–6.2). Normalization of IGF-1 was observed in 96%, with an IGF-1 of 17.9 nmol/l (13.0–23.8) and a ratio IGF-1 of 0.6 (0.4–0.7). At the last visit, weekly PEGV dose of 80 mg (60–120 mg) was used during combination treatment with LA-SRIFs. In patients with mono-therapy a weekly PEGV dose of 210 mg (125–280 mg) was used. No significant differences in PEGV dose, needed to control IGF-1 were observed between sexes, diabetic/non-diabetic patients, surgery/non-surgery and Gilberts polymorphism/non-Gilberts polymorphism.

Baseline GH levels (on LA-SRIFs) were not significantly different compared with GH during PEGV and LA-SRIFs treatment (P=0.567). Two subgroups were defined according to surgical status (surgery vs non-surgery). After surgery GH seem to decrease during treatment (8.7 and 4.5 nmol/l), while primary medical treatment GH seem to increase (4.0 and 4.5 nmol/l), although not significantly different (P=0.091 (post-radiotherapy-group was excluded)).

Conclusion: Combination of LA-SRIF and PEGV in acromegaly is effective up to 8 years, with an efficacy of 96%. GH levels do not change during treatment.