In vivo gastrin releasing peptide receptor expression in SDH deficient wild-type gastrointestinal stromal tumours (GIST): potential for theranostic applications.

BACKGROUND

Succinate dehydrogenase (SDH) deficient wild-type Gastrointestinal Stromal Tumours (wtGIST) are a rare GIST subtype with limited treatment options. Gallium-68 labelled Gastrin Releasing Peptide Receptor (GRPR) antagonist NeoB has shown promise in PET imaging for multiple primary malignancies. This investigation sought to assess the biodistribution of [68Ga]NeoB via PET/CT imaging in metastatic wtGIST patients and aimed to evaluate GRPR expression in lesions to determine the ligand's potential for patient selection in future therapeutic trials.

RESULTS

Twelve patients with histologically confirmed metastatic wtGIST were enrolled. [68Ga]NeoB PET/CT imaging was conducted for lesion segmentation and analysis of uptake characteristics. 8 of 12 (66.7%) patients exhibited intense but heterogeneous [68Ga]NeoB uptake in lesions, with variable tracer uptake both within and between lesions. Physiological uptake was highest in the pancreas, liver, and spleen. Four patients (33.3%) displayed minimal or no uptake in tumour lesions.

CONCLUSIONS

The majority of wtGIST patients in this small cohort show lesions with intense [68Ga]NeoB uptake. Heterogeneity of uptake indicates GRPR has highly variable inter- and intralesional expression. NeoB has potential for theranostic application in wtGIST, with limited effective standard of care treatments available. Ongoing trials are investigating the therapeutic use of [177Lu]NeoB in this setting.

CLINICAL TRIAL NUMBER: Not applicable.