Endocrine Abstracts

JOINT2141

Background: Pasireotide LAR is a long-acting somatostatin analog with potential antitumor activity, as demonstrated by treatment induced increased MRI T2-signal intensity of somatotrophic PitNETs (1), but long-term follow-up data are lacking.

Aim: To investigate pasireotide’s long-term antitumor effect and the impact on clinical outcomes in acromegaly patients.

Methods: We included participants from the previously published PAPE study (2) and evaluated clinical outcomes, medication use, and PitNET characteristics on MRI over the past 10 years. T2-weighted MRI signals of the PitNETs using grey matter as a reference were quantified and PitNET volumes and T2-intensity ratios (IRs) were calculated for each scan.

Results: Forty-four patients, 43 % female, median (IQR) age 52 (15 years) were included. Median treatment duration was 31.0 months. The median IR of the PitNETs increased between baseline and MRI at 7 years (1.09 vs. 1.57, P < 0.001), indicating cystic degeneration. In addition, a reduction in PitNET volume was observed between baseline and each subsequent follow-up MRI, with a more than twofold reduction in median volume between baseline and MRI at 7 years (1607 vs. 762 mm³, P = 0.03). In 12 patients (27.3%), acromegaly treatment was reduced based on decreasing IGF-1 levels without presence of surgery or radiotherapy.

Conclusion: Pasireotide induces a long-term cystic degeneration process in somatotrophic PitNETs that persists for several years after treatment discontinuation. This phenomenon expands pasireotide’s therapeutic applications by utilizing it as a potential preoperative treatment to enhance surgical outcomes.

References: 1. Coopmans EC et al. Potential antitumour activity of pasireotide on pituitary tumours in acromegaly. Lancet Diabetes Endocrinol. 2019;7(6):425-6.

2. Muhammad A, et al. Efficacy and Safety of Switching to Pasireotide in Patients With Acromegaly Controlled With Pegvisomant and First-Generation Somatostatin Analogues (PAPE Study). J Clin Endocrinol Metab. 2018;103(2):586-95.