Real-World Experience With Pasireotide Lar in Acromegaly Resistant to First-Generation Somatostatin Analogs: A Single Center 1-Year Observation

Introduction: First generation somatostatin analogs (SSAs) are the treatment of choice in persistent acromegaly after transsphenoidal surgery. However, they are effective in 25% to 45 % of patients and a second generation SSA - pasireotide LAR may be a more effective alternative. Aim Our aim was to evaluate the impact of 1-year treatment with pasireotide LAR on disease control and on glucose metabolism in patients with acromegaly after debulking surgery resistant to first-generation SSAs. Material and methods In this single-center prospective study 29 consecutive patients with resistant acromegaly were treated with pasireotide LAR. The initial drug dose was 40 mg i.m. every 28 days. If patient did not achieve biochemical control (GH <2.5 ng/mL and IGF-1 ≤ULN for age and sex) at month 3, the dose was increased to 60 mg i.m. every 28 days. Assessment (GH, IGF-1, glucose, HbA1c) was performed at month 3, 6, 9 and 12. Results: In total, 22 patients (10 females, 12 males) completed a 1-year treatment. Mean age was 41.8±13.8 years. Twelve patients (54.5%) were ≤ 40 years old (including 6 (27.3%) patients of age ≤30 years). At baseline, mean IGF-1 level was 2.3 (SD 0.7) x ULN (age- and sex-specific) (583.9 ng/mL; SD 182.2) and mean GH concentration was 3.9 (SD 2.8) ng/mL. Both values decreased significantly after 1 year of treatment (P<0.001). Pasireotide LAR dose was increased to 60 mg in 16 (72.7%) patients and decreased to 20 mg in one patient patient due to worsening of diabetes control. The magnitude of mean GH level decrease was the largest within first 6 months (mean change from baseline: -1.75 ng/mL, 95% CI: -2.64, -0.85, P=0.0006). Mean IGF-1 level decreased rapidly within the first 3 months (mean change from baseline: -153.20 ng/mL, 95% CI: -203.20, -103.19, P<0.0001) and remained low during 12-month follow-up. GH level ≤ 1 ng/mL and ≤2.5 ng/mL was achieved by 7 (31.8%) and 17 (77.3%) patients, respectively. Six patients (27.3%) achieved normal IGF-1 level (IGF-1 ≤1 x ULN) (P=0.0275). IGF-1 ≤1.3 x ULN was observed in 11 (50.0%) of patients. Full biochemical control (GH ≤1 ng/mL and IGF-1 ≤1 x ULN) was achieved in 3 (13.6%) patients. Pasireotide LAR treatment resulted in significant increase of mean fasting glucose level: 119.2 (SD 17.3) vs. 107.5 (SD 13.9) mg/dL, P<0.001. The largest change was observed in first 3 months, and it remained stable until month 12. HbA1c level also increased significantly during first 3 months and stayed on similar level during follow-up (mean for month 12: 6.3 (SD 0.6) vs. 5.9 (SD 0.5) % at baseline, P<0.001). Conclusions: Pasireotide LAR is an effective treatment in most patients with persistent acromegaly after surgical debulking resistant to first generation SSAs. The largest increase of glycemia occurs during first 3 months of treatment and it remains stable afterwards.