Effectiveness of peptide receptor radionuclide therapy for neuroendocrine neoplasms; a multi-institutional registry study with prospective follow up

Aims: Peptide receptor radionuclide therapy targets somatostatin receptors expressed on well differentiated neuroendocrine neoplasms. Retrospective monocentric studies indicate that peptide receptor radionuclide therapy is an effective treatment for patients with neuroendocrine neoplasms.

Patients and methods: We initiated a multi-institutional, prospective and board reviewed registry for patients treated with peptide receptor radionuclide therapy. 450 patients were included and followed for a mean of 24.4 months. Patients were treated with Lutetium-177 (54%), Yttrium-90 (17%) or both radionuclides (29%). Primary neuroendocrine neoplasms were derived of pancreas (38%), small bowel 30%), unknown primary (19%), lung (4%) and colorectum (3,5%). Most neuroendocrine neoplasms were well differentiated with a proliferation rate below 20% in 54% and were pretreated by 1 or more therapies in 73%.

Results: Overall survival of all patients from the beginning of therapy was 59 months in median. Median survival depended on radionuclides used (Yttrium-90: 38 months; Lutetium-177: not reached; both: 58 months), proliferation rate (G1: median not reached; G2: 58 months; G3: 33 months; unknown: 55 months) and origin of primary tumors (pancreas: 53 months; small bowel: not reached; unknown primary: 47 months; lung: 38 months) but not upon number of previous therapies. Median progression-free survival measured from last cycle of therapy accounted to 41 months for all patients. Progression-free survival of pancreatic neuroendocrine neoplasms was 39 months in median. Similar results were obtained for neuroendocrine neoplasms of unknown primary with a median of 38 months whereas neuroendocrine neoplasm of small bowel were progression-free for a median of 51 months. Side effects like G3-G4 nephrotoxicity or hematological function were observed in 0.2% and 2% of patients.

Conclusion: These results indicate that peptide receptor radionuclide therapy is an effective therapy for patients with G1-G2 neuroendocrine tumors irrespective of previous therapies with a survival advantage of several years compared to other therapies and only minor side effects.