Organ-specific response to [177Lu]DOTATATE peptide receptor radionuclide therapy (PRRT) assessed by sequential [68Ga]DOTATOC PET/CT in patients with metastatic small intestine neuroendocrine tumors.

PURPOSE: To evaluate organ-specific response to [177Lu]DOTATATE Peptide Receptor Radionuclide Therapy (PRRT) in patients with small intestine neuroendocrine tumor (SiNET) through [68Ga]DOTATOC PET/CT, and to analyze tumor uptake and functional volume variations at different metastatic sites in relation to disease progression during clinical follow-up after treatment.

METHODS

A retrospective analysis was conducted on 33 metastatic patients. PET/CT were performed pre-treatment (PET0), mid-treatment after two PRRT cycles (PET2), and post-treatment (PET4). SUVmax and somatostatin receptor-expressing tumor volume (SRETV) were measured in liver, lymph node, peritoneum/mesentery, and bone metastases.

RESULTS

Liver metastases showed significant reduction in both SUVmax and SRETV from PET0 to PET4, with early response evident after two PRRT cycles. Nodal lesions exhibited a delayed response, with significant reductions at PET4. Peritoneal and bone metastases showed a continuous decline in SUVmax, but no significant changes in SRETV. Objective response rates were highest in liver metastases after treatment completion with lesser responses in nodal, peritoneal, and bone lesions. At a median follow-up of 24.3 months, 70% of patients experienced disease progression, while 30% did not. Liver metastases showed no significant changes in SUVmax or SRETV regardless of progression. Conversely, in non-progressing patients, peritoneal/mesenteric lesions showed a significant reduction in SUVmax, with unchanged SRETV, and nodal metastases exhibited reduced SRETV. Bone lesions in non-progressing patients showed significant decreases in both SUVmax and SRETV.

CONCLUSION

[177Lu]DOTATATE PRRT effectively reduces tumor functional activity in patients with SiNETs, with organ-specific responses highlighting the need for personalized treatment strategies to optimize efficacy and minimize toxicity.