Background: The response to first-generation somatostatin receptor ligands (SRLs) treatment in acromegaly correlates with expression of somatostatin receptor subtype 2 (SSTR2). However, pasireotide shows the highest binding affinity for SSTR subtype 5 (SSTR5). It has been suggested that in acromegaly, SSTR5 expression is better at predicting the response to pasireotide long-acting release (PAS-LAR) treatment than SSTR2 expression. Aim: To investigate in patients with active acromegaly whether response to SRL treatment correlates to PAS-LAR treatment and to what extent SSTR2 and SSTR5 expression are correlated to the response to PAS-LAR treatment. Methods: We included 52 patients from a cohort that initially received SRL treatment, followed by SRL and pegvisomant combination treatment, and finally PAS-LAR treatment. The long-term response to PAS-LAR was evaluated using a PAS-LAR score. In 14 out of 52 patients, somatotroph adenoma tissue samples were available to evaluate SSTR2 and SSTR5 expression using a previously validated immunoreactivity score (IRS). Results: The percentage IGF-I (times the upper limit of normal) reduction, which was observed after SRL treatment, correlated with PAS-LAR response score during follow-up (r = 0.40; P = 0.003; n = 52). After exclusion of SRL-pretreated patients, SSTR2 IRS was positively correlated to PAS-LAR score (r = 0.58; P = 0.039; n = 9), whereas SSTR5 IRS showed no relation (r = 0.35; P = 0.36; n = 9). Conclusions: In a cohort of patients partially responsive to SRLs, the IGF-I–lowering effects of PASLAR treatment correlated with the effect of SRL treatment and seemed to be mainly driven by SSTR2 expression instead of SSTR5.,
Journal of Clinical Endocrinology and Metabolism
Department of Radiology

Muhammad, A., Coopmans, E.C., Gatto, F, Franck, S.E, Janssen, J.A.M.J.L, Lely, A.J.D., … Neggers, S.J.C.M.M. (2019). Pasireotide Responsiveness in Acromegaly Is Mainly Driven by Somatostatin Receptor Subtype 2 Expression. Journal of Clinical Endocrinology and Metabolism, 104(3), 915–924. doi:10.1210/jc.2018-01524