Normal Insulin-like Growth Factor 1 During Somatostatin Receptor Ligand Treatment Predicts Surgical Cure in Acromegaly.

Abstract

Treatment with somatostatin receptor ligands (SRLs) is often given before pituitary surgery to patients with acromegaly. To study whether the response to treatment with SRLs is predictive of surgical outcome. Retrospective, observational study. Tertiary care center. We investigated 272 patients with acromegaly who had been treated with an SRL between 1990 and 2018. All patients underwent pituitary surgery performed by a skilled neurosurgeon. Outcome of pituitary surgery in patients who had normalization of insulin-like growth factor 1 (IGF-1) levels during SRL therapy in comparison with patients who did not normalize IGF-1 levels. Normalization of IGF-1 levels during SRL treatment occurred in 62 patients (22.8%) and was similar for the 3 different types of SRL (P = .88). Surgical remission occurred in 59.6% of the patients. Patients who normalized IGF-1 levels during SRL treatment had a higher probability of surgical cure than patients without IGF-1 normalization (83.9% vs 52.4%, respectively; P < .001). Multivariate analysis confirmed that lack of cavernous sinus invasion, small maximum tumor diameter, and IGF-1 normalization during SRL therapy were the only factors independently associated with a favorable surgical outcome. Our study demonstrates that the normalization of IGF-1 levels during treatment with SRLs is an independent predictive factor of a favorable surgical outcome. The underlying mechanisms remain unclear, but an optimal response to medical therapy may be a characteristic of less aggressive tumors that are more likely to be entirely removed at surgery.