Purpose: Increased glycolytic activity on FDG PET/CT defines a subgroup of patients with metastatic gastroenteropancreatic neuroendocrine tumour (NET) with a poor prognosis. A limited range of systemic treatment options exist for more aggressive NET. The role of peptide receptor chemoradionuclide therapy (PRCRT) in such patients is, however, unclear. This retrospective study assessed the outcomes of patients with FDG-avid NET treated with PRCRT.
Methods: Clinical, biochemical and imaging response was assessed after completion of induction treatment of PRCRT with 5-fluorouracil in 52 patients selected for treatment on the basis of somatostatin-receptor imaging without spatially discordant FDG-avid disease. Of the cohort, 67% had received prior chemotherapy. Overall survival (OS) and progression-free survival (PFS) were also analysed.
Results: PRCRT was well tolerated with negligible grade 3/4 toxicities. After a median follow-up period of 36 months, the median OS was not achieved with a median PFS of 48 months. At 3 months after completion of PRCRT 2% of patients showed a complete anatomical response, 28% a partial response, 68% stable disease, and only 2% progression. On FDG PET/CT, 27% achieved a complete metabolic response during the follow-up period. A biochemical response (>25% fall in chromogranin-A levels) was seen in 45%.
Conclusion: PRCRT is an effective treatment in patients with FDG-avid NET, even in patients who have failed conventional therapies. Given apparently higher response rates than with alternative therapeutic options and low toxicity, further research is needed to establish whether PRCRT should be used as a first-line treatment modality in this patient population.