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

CONTEXT: Treatment with somatostatin receptor ligands (SRLs) is often given before pituitary surgery to patients with acromegaly.

OBJECTIVE: To study whether the response to treatment with.SRLs is predictive of surgical outcome.

DESIGN: Retrospective, observational study.

SETTING: Tertiary care center.

PATIENTS: We investigated 272 patients with acromegaly who had been treated with an SRL between 1990 and 2018.

INTERVENTION: All patients underwent pituitary surgery performed by a skilled neurosurgeon.

MAIN OUTCOME MEASURE: 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.

RESULTS: Normalization of IGF-1 levels during SRL treatment occurred in 62 patients (22.8%) and was similar for the three 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.

CONCLUSIONS: 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.