Romy van der Groef¹, Sophie Veldhuijzen-van Zanten², Julie Refardt³, Sebastian Neggers⁴


(1) Erasmus MC, Internal Medicine section endocrinology, Rotterdam, Netherlands. (2) Erasmus MC, Department of Radiology and Nuclear Medicine, Rotterdam, Netherlands. (3) Erasmus MC, Internal Medicine section endocrinology, Rotterdam, Netherlands. (4) Erasmus MC, Internal Medicine section endocrinology, Rotterdam, Netherlands.

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 ver 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:

Twenty-eight patients, 61 % female, median (IQR) age 52 (19 years) were included. The median treatment duration was 16.5 months. Median IR of the PitNETs increased between baseline and MRI at 7 years (1.02 vs. 1.48, p<0.001), indicating cystic degeneration. In addition, a significant reduction in PitNET volume was observed between baseline and each subsequent follow-up MRI, with a fourfold reduction in median volume between baseline and MRI at 7 years (239 vs. 474 mm³, p=0.006). In 10 patients (35.7%), 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.