Endocrine Abstracts

Background: In PRIMARYS, lanreotide Autogel (LAN) 120 mg/28 days reduced tumour volume (TV), and GH/IGF-1 levels in patients with GH-secreting macroadenomas. In post-hoc analyses, we investigated predictive factors for treatment responses.

Methods: PRIMARYS, a 48-week, international, open-label study, involved 90 treatment-naïve patients with GH-secreting macroadenomas receiving LAN. Factors predictive for hormonal control (HC; GH ≤2.5 μg/L+ normal IGF-1) at last post-baseline value available (LVA) or ≥20% TV reduction (TVR) at week 48/LVA were investigated using univariate logistic regression. Week-12 GH, IGF-1 and TV cut-off values for predicting responses were obtained from ROC curves, maximising the Youden index. Analyses used intention-to-treat populations and P<0.05 as significant.

Results: From univariate analyses, HC was more likely in women (odds ratio: 2.9 times higher for women vs. men), and older patients (2.2 times higher for each 10-year higher age), and with lower baseline IGF-1 (1.1 times higher for each 10% lower IGF-1 level [% upper limit of normal, ULN]), but no association with GH levels was shown. HC was determined by week-12 hormonal response: optimal cut-offs were 1.19 μg/L for GH (sensitivity, 0.79; specificity, 0.89; area-under-the-curve [AUC] value, 0.87) and 110% ULN for IGF-1 (0.89, 0.85 and 0.93, respectively). Univariate analyses revealed no baseline factors influencing TVR. TVR was, however, determined by changes from baseline to week 12 in GH, IGF-1 and TV: optimal cut-offs were −69% for GH (sensitivity, 0.74; specificity, 0.67; AUC, 0.74), −61% for IGF-1 (0.58, 0.80, 0.75), and −21% for TV (0.81, 0.97, 0.93).

Conclusions: Based on post-hoc PRIMARYS data, treatment-naïve patients with GH-secreting macroadenomas are more likely to achieve long-term hormonal control with LAN 120 mg/28 days if GH levels are <1.2 μg/L and IGF-1 levels <110% ULN at 12 weeks, and more likely to achieve clinically significant long-term reductions in TV with >60% reductions in GH/IGF-1 levels by week 12.