Long-Term Antitumour Effects of Pasireotide in Acromegaly.

Pasireotide LAR, a long-acting somatostatin receptor ligand, has shown potential antitumour activity in somatotroph pituitary tumours, as indicated by increased T2-signal intensity on 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. Retrospective cohort study. Patients from the previously published PAPE study were included. Over the course of eight-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. 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 < 0.001), indicating progressive cystic degeneration. Tumour volume significantly declined over time, with a median reduction from 1239 mm³ to 603 mm³ (p = 0.005). Importantly, 12 patients (27.3%) experienced a reduction in medical acromegaly treatment, without the need for surgery or radiotherapy due to decreasing IGF1 levels. 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.