IGF-I levels during standard Lanreotide dose predicts biochemical outcome of high-frequency regimen in acromegaly

Introduction: First-generation somatostatin receptor ligands (fg-SRLs) are the cornerstone of acromegaly treatment. Additional benefits were shown using high dose (HD) or high frequency (HF), relatively short-term regimens. Although several predictors of response to standard dose (SD)-fg-SRLs were reported, outcome biomarkers for HF administration are not yet available. Here, we aimed to identify predictors of response to long-term HF-fg-SRLs. Patients and methods: A retrospective study was performed on 102 patients, treated with Lanreotide. Patients not controlled at 12 months of SD-Lanreotide (120 mg/28 days) were switched to HF-Lanreotide (120 mg/21 days) for additional 12 months. Results: Twenty-eight patients were controlled at 6 months of SD-Lanreotide (27.4%); 35 patients were controlled at 12 months of treatment (34.3%). Out of 67 patients treated with HF- Lanreotide, 18 (26.9%) were controlled at 6 months of treatment and remained controlled until 12 months. Both during SD and HF-Lanreotide administrations, IGF-I levels were reduced during the first six months of treatment (p < 0.001), without further significant reduction between 6 and 12 months of therapy. Response at 12 months of SD-Lanreotide was predicted by IGF-I reached at six months of SD-Lanreotide (p = 0.024). Response at 12 months of HF-Lanreotide treatment was predicted by IGF-I levels reached at six months of SD-Lanreotide treatment (p = 0.04) and six months of HF-Lanreotide treatment (p = 0.01). Conclusion: Our results demonstrated that initial IGF-I levels during SD-Lanreotide predicted the biochemical outcome after 12 months of HF-Lanreotide. Patients in whom HF-Lanreotide did not normalize IGF-I after 6 months of treatment remained uncontrolled 12 months after starting this regimen.