Purpose: The European Neuroendocrine Tumor Society (ENETS) guidelines advocate a right hemicolectomy (RHC) only in patients with appendiceal neuroendocrine neoplasms (aNENs) at risk for N+(node positive). The risk is defined using site, size, and grading of tumor as well as mesoappendiceal or lymphovascular invasion.
Methods: A systematic review and meta-analysis was carried out. The data were reported using risk difference (RD) to define the risk of N+. The number needed to treat/harm (NNT/NNH) and the likelihood of being helped or harmed (LHH) were calculated using RD. Two strategies were considered: "to treat all" versus "to treat only patients having aNENs with risk stigmata". The aim was to evaluate the harm/benefit ratio related to the use of the ENETS lymph-nodal metastases (N+) risk factors.
Results: Six studies were included involving a total of 261 patients. The RD (-0.30; P < 0.001) of N+ was significantly lower in aNENs ≤ 20 mm as compared to those >20 mm. One unnecessary RHC every five patients (NNT = 5) could be avoided while 1 patient with N+ every six patients (NNH = 6) remained untreated. The risk was lower than the benefits (LHH = 1.2). The RD NNT, NNH, and LHH values suggested that only a 15 mm cutoff and the presence of lymphovascular invasion could be considered useful.
Conclusions: An RHC should be performed in patients with aNENs >20 mm. The use of a 15 mm cutoff criterion had a similar outcome to that of a 20 mm cutoff. Lymphovascular invasion should only be considered a minor criterion. Selection based on other parameters should be avoided.
Keywords: Appendix; Carcinoid; Neuroendocrine tumor.