Oligometastatic neuroendocrine tumors: characteristics and prognosis

Oligometastatic disease (OMD) in neuroendocrine tumors (NET) has hardly been investigated so far and it is unclear how OMD should influence treatment decisions.

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.

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).

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.