The role of an acute pasireotide suppression test in predicting response to treatment in patients with Cushing's disease: findings from a pilot study.

Pasireotide is a multireceptor-targeted somatostatin analog effective in the treatment of Cushing's disease (CD). We evaluate the value of an acute pasireotide suppression test (PST) in predicting response to medium/long-term treatment in CD. Nineteen patients with active CD were prospectively investigated at two referral centers from May 2013 to August 2014. Follow-up data (median 6 months; range 1-9 months) were available for sixteen patients. All patients received at 09:00 h a single subcutaneous (sc) injection of 600 μg pasireotide. Serum cortisol and plasma ACTH were assessed before, and every 2 h for 8 h after, drug administration. Late-night salivary cortisol (LNSC) was assessed before and after pasireotide administration. After acute PST, all patients were continued on pasireotide 600 μg sc twice a day. During PST, cortisol and ACTH levels quickly decreased in all patients except one with a mean percentage fall, respectively, of 48.9 ± 24.3 and 48.1 ± 25.4 % compared to baseline. LNSC decreased in about 82 % of patients (14/17) achieving a normalization in five of them. Pasireotide treatment was associated with a normalization of 24-h urinary-free cortisol at last follow-up in about 68 % of patients. A fall >27 % of LNSC during PST calculated by ROC curve was the best parameter in predicting a positive response to treatment with pasireotide (sensitivity 91 %; specificity 100 %; positive predictive value 100 %; negative predictive value 75 %). Acute PST may be useful to identify CD patients who will benefit from pasireotide treatment. A LNSC fall >27 % as well as a LNSC normalization during PST is associated with a probability of 100 % of achieving a favorable response to pasireotide treatment in the medium/long term.