Follow-up recommendations after curative resection of well-differentiated Neuroendocrine Tumours: review of current evidence and clinical practice

The incidence of neuroendocrine neoplasms (NENs) is increasing, especially for patients with early stages and grade 1 tumours. Current evidence also shows increased prevalence, probably reflecting earlier stage diagnosis (e.g. at the time of endoscopy) and improvement of treatment options.
Definition of adequate post-surgical follow-up for NENs is a current challenge. There are limited guidelines and heterogeneity in adherence to those available is notable.
Unfortunately, the population of patients at greatest risk of recurrence has not been defined clearly. Some studies support that for patients with pancreatic neuroendocrine tumours (PanNETs), factors such as primary tumour (T), stage, grade (Ki-67), tumour size and lymph node metastases (N) are of relevance. For bronchial (LungNETs) and small intestinal (siNETs), similar factors have been identified.
This review summarises the evidence supporting the rationale behind follow-up after curative resection in well-differentiated PanNETs, siNETs and LungNETS. Since surgery for poorly-differentiated tumours has a limited role, the focus of these recommendations will be limited to patients with well-differentiated tumours. Published evidence informing relapse rate, disease-free survival and relapse patterns are discussed, together with an overview of current guidelines informing post-surgical investigations and duration of follow-up.