Background: A low burden of disease represents an independent favorable prognostic factor of response to peptide receptor radionuclide therapy (PRRT) in patients affected by gastro-entero-pancreatic neuroendocrine tumors. However, it is not clear whether this is due to a lower diffusion of the disease or thanks to debulking surgery.
Methods: From 1996 to 2013 those patients diagnosed with G1-G2 pancreatic neuroendocrine tumor (PNET) and synchronous liver metastases who were not deemed eligible for liver radical surgery but were eligible to receive upfront PRRT were prospectively included in the study. Two groups of comparison were identified: those submitted for primary tumor resection before PRRT and those who were not. The outcome was evaluated as: objective response to PRRT (OR), progression-free survival (PFS), and overall survival (OS).
Results: Of the 94 subjects, 31 were previously submitted for primary tumor resection. After propensity score adjustments, patients who underwent surgery before PRRT showed higher stabilization or objective responses after PRRT (p = .006), and this translated into a better median PFS (70 vs. 30 months; p = .002) and OS (112 vs. 65 months; p = .011), for operated versus nonoperated patients, respectively. At multivariate analysis, operated patients showed a statistically significantly improved PFS: HR, 5.11 (95 % CI 1.43-18.3); p = .012, whereas Ki-67 in continuous fashion was correlated significantly with OS: 1.13 (95 % CI 1-1.27); p = .048.
Conclusions: Primary tumor resection prior to PRRT can be safely proposed in G1-G2 PNETs with diffuse liver metastases because it seems to enhance response to PRRT and to improve significantly PFS.