Dual-tracer PET/CT with [68Ga]Ga-DOTATATE and [18F]F-FDG identified unusual gastric metastases in recurrent pancreatic NET, guiding theranostic strategy

Recurrence of pancreatic neuroendocrine tumors (NET) after surgical resection presents a significant clinical challenge, often requiring advanced imaging for accurate staging and treatment planning. While local recurrence is common, distant metastases can occur in unusual sites, making detection difficult with conventional imaging. Gastric metastases from NETs are particularly infrequent, yet their presence can significantly alter prognosis and therapeutic strategies. The use of somatostatin receptor-based imaging, like [68Ga]Ga-DOTATATE-PET/CT, is crucial for identifying NET lesions, but assessing tumor aggressiveness often requires metabolic imaging such as [18F]F-FDG-PET/CT to guide optimal theranostic approaches.

This case report details a patient with recurrent pancreatic NET who developed unusual gastric wall metastatic disease after a prolonged progression-free period following primary tumor resection. The patient underwent comprehensive diagnostic imaging using both [68Ga]Ga-DOTATATE-PET/CT and [18F]F-FDG-PET/CT. The primary endpoint was to identify the site and metabolic activity of the recurrent disease to inform subsequent therapeutic decisions. The dual-tracer approach aimed to provide a complete picture of both somatostatin receptor expression and glucose metabolism within the metastatic lesions.

The [68Ga]Ga-DOTATATE-PET/CT scan successfully identified the recurrence of pancreatic NET as distinct lesions within the gastric wall, an unusual metastatic site. This finding was critical as it confirmed the presence of somatostatin receptor-positive disease suitable for targeted therapies. Concurrently, the [18F]F-FDG-PET/CT revealed significant [18F]F-FDG avidity in these same gastric lesions. This [18F]F-FDG uptake is a key indicator of increased glucose metabolism, suggesting a more aggressive tumor phenotype. > The dual-tracer imaging strategy proved instrumental in characterizing the recurrent disease, indicating the necessity of a combined therapeutic approach involving chemotherapy and [177Lu]Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) due to the mixed somatostatin receptor expression and high metabolic activity.