Long-term antitumour effects of pasireotide in acromegaly

Objective: Pasireotide long-acting release (LAR), a long-acting somatostatin receptor ligand, has shown potential antitumour activity in somatotroph pituitary tumours, as indicated by increased T2-signal intensity on magnetic resonance imaging (MRI). However, long-term follow-up data on its effects are limited. This study aimed to evaluate the long-term antitumour effects of pasireotide and its impact on clinical outcomes in patients with acromegaly. Design: The design is a retrospective cohort study. Methods: Patients from the previously published PAPE study were included. Over the course of 8 years, clinical outcomes, medication use, and tumour characteristics were assessed. T2-weighted MRI signals of tumours were analysed using grey matter as the reference region, and tumour volumes along with T2-intensity ratios (IRs) were calculated from all available scans. Results: Forty-four patients [57% male; median age 52 years (IQR 15)] were included. The median duration of pasireotide treatment was 31.0 months. From baseline to the 8-year follow-up, the median T2-IR increased from 1.03 to 1.56 (P < .001), indicating progressive cystic degeneration. Tumour volume significantly declined over time, with a median reduction from 1239 to 603 mm³ (P = .005). Importantly, 12 patients (27.3%) experienced a reduction in medical acromegaly treatment, without the need for surgery or radiotherapy due to decreasing insulin-like growth factor 1 (IGF1) levels. Conclusions: Pasireotide appears to induce durable cystic degeneration in somatotroph tumours, with evidence suggesting sustained antitumor effects that may extend beyond treatment discontinuation. These findings support its potential for a broader therapeutic role, warranting validation in future prospective studies.