The treatment with pasireotide in Cushing's disease: effects of long-term treatment on tumor mass in the experience of a single center

Abstract

Pasireotide is the first medical therapy officially approved for the treatment of adult patients with Cushing's disease (CD) who experienced a failure of pituitary surgery or are not candidates for surgery and require medical therapeutic intervention. The current study aimed at investigating the effects of long-term treatment with pasireotide (up to 24 months) on tumor mass in a group of patients with CD, participating to a phase III study. Fourteen CD patients entered the phase III clinical trial CSOM230B2305 at Naples Center, and eight (seven women, one man, aged 38.9 ± 17.6 years), including seven with a microadenoma and one with a macroadenoma, received treatment with pasireotide at the dose of 600-1200 µg bid for at least 6 months, and were considered for the analysis of the study. These eight patients were subjected to the evaluation of pituitary tumor volume by pituitary MRI, together with the evaluation of urinary cortisol levels, at baseline and every 6 months for the entire period of treatment. Pasireotide treatment induced full disease control in 37.5 % and partial disease control in 37.5 % after 6 months, whereas full and partial disease control after 12 months was obtained in 28.6 % and in 57.1 % of patients, respectively. A significant (>25 %) reduction in tumor volume was found in 62.5 % and in 100 % of patients, after 6 and 12 months, respectively. In particular, after 6 months, a slight tumor shrinkage (between 25.1 and 50 %) was observed in 25 %, moderate (50.1-75 %) in 25 %, and marked (>75 %) in 12.5 % of patients, whereas after 12 months, a slight tumor shrinkage was observed in 43 %, moderate in 14 %, and marked in 43 % of patients. In 25 % of patients (two patients), a marked tumor shrinkage was recorded, with tumor mass disappearance in one case; this tumor shrinkage was associated to rapid and sustained biochemical remission up to 24 months of continuous pasireotide treatment. These two cases represent the first cases with a documentation of such a notable effect of pasireotide on tumor mass. Pasireotide induces significant tumor shrinkage in 62.5 % of patients after 6 months and in 100 % of patients after 12 months, and occasionally induces a radiological disappearance of the tumor. This evidence supports and strengthens the role of pasireotide as medical treatment specifically addressed to patients with CD, particularly in those who had unsuccessful pituitary surgery, or are not candidates for surgery.

Keywords: ACTH-secreting pituitary tumor; Cushing’s disease; Cushing’s syndrome; Pasireotide; Somatostatin analogs; Tumor mass.