Oligometastatic neuroendocrine tumors: characteristics and prognosis

INTRODUCTION: Oligometastatic disease (OMD) in neuroendocrine tumors (NET) has hardly been investigated so far and it is unclear how OMD should influence treatment decisions. METHODS: The primary objective of this retrospective analysis was to evaluate characteristics and prognosis of the OMD state in patients with NET G1/G2 of gastroenteropancreatic origin. RESULTS: The overall study cohort comprised 190 patients. OMD occurred in 29% of patients (n = 55), 58% of those (n = 32) had synchronous oligometastases. Oligometastases were limited to one organ in most patients (95%) and primarily involved the liver (83% or n = 43/52). Median overall survival (OS) from diagnosis was 117.5 months (95% CI 102.4-149.1 months). Calculated from first metastasis, median OS was 102.4 months (95% CI 98.3-117.5 months) and not significantly longer in oligometastatic patients (117.5 months) versus polymetastatic patients (100.2 months). Locoregional treatment of oligometastases was performed in 24/55 patients (44%) and showed a non-significant trend towards superior survival compared to no such treatment (125.4 versus 99.7 months). CONCLUSIONS: These results suggest that a low absolute number of metastases alone may not be a clear prognostic factor in NET. It remains unknown if locoregional therapies can achieve long-term disease-free survival in a significant number of oligometastatic NET patients.