EYES2019 7th ESE Young Endocrinologists and Scientists (EYES) Meeting Oral Presentations (67 abstracts)
1Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, The Netherlands; 2Department of Radiology, Erasmus University Medical Center, Rotterdam, The Netherlands; 3Department of Biostatistics, Erasmus MC, Rotterdam, The Netherlands; 4Department of Endocrinology, Centre Hospitalier Universitaire de Liège, Domaine Universitaire du Sart Tilman, Liège, Belgium; 5Department of Clinical Chemistry, Erasmus University Medical Center, Rotterdam, The Netherlands.
Objective: MRI T2-signal intensity and somatostatin (SST) receptor expression are recognized predictors of therapy response in acromegaly. We investigate the relationship between these predictors and the hormonal and tumor responses to PAS-LAR therapy, and compare to first-generation somatostatin receptor ligands (SRLs) responsiveness.
Methods: We included 45 acromegalics initially receiving SRLs, followed by a combination therapy including pegvisomant (PEGV), and finally PAS-LAR. Primary endpoints were tumor volume reduction (≥25% from baseline) and IGF-I levels (expressed as upper limit of normal (ULN)) during three months of PAS-LAR. We assessed T2-weighted MRI signal intensity by region of interest (ROI), visual assessment, SST receptor expression and IGF-I reduction (%) after SRLs.
Results: Significant tumor shrinkage was observed in patients with less IGF-I reduction during SRLs (mean 18.6% [S.D. 24.4] vs 35.1% [23.0], P=0.036), higher IGF-I levels during PAS-LAR (mean 1.36 [S.D. 0.53] vs 0.93 [0.43], P=0.020) and adenomas with low SST2 receptor expression (median 2.0 [IQR 1.06.0] vs 12.0 [7.512.0], P=0.040). Lower IGF-I levels during PAS-LAR were associated with higher T2-signal intensity (ß −0.29, 95% CI −0.56−0.01). Patients with PAS-LAR-induced increased T2-signal intensity, achieved lower IGF-I levels (median 0.84 [IQR 0.511.28] vs 1.10 [0.821.30], P=0.047), while harboring relatively larger adenomas during PAS-LAR (median 1719 [IQR 11434616] vs 574 [1702190], P=0.050).
Conclusions: Patients unresponsive to SRLs with low SST2 receptor expression are more prone to achieve tumor shrinkage during PAS-LAR. Surprisingly, tumor shrinkage is not accompanied by achieving lower IGF-I levels, which are associated with higher T2-signal intensity.