Should surgery be conducted for small nonfunctioning pancreatic neuroendocrine tumors: a systematic review

BACKGROUND: The incidence of nonfunctioning pancreatic neuroendocrine tumors smaller than 2cm has increased remarkably in the last two decades. Controversies exist regarding whether surgery should be conducted for this group of tumors. METHODS: MEDLINE, EMBASE and CENTRAL were search until 2017/01/17. Studies with comparative results between operation and observation group were included. Primary outcomes were overall survival and disease specific survival. Secondary outcomes were disease progression and surgical death and complications. RESULTS: 6 studies with a total of 1861 patients were identified. No randomized controlled trials were found. Survival rate was high (97-100%) and no patients died because of the disease in 5 of the 6 studies, with no difference between operation and observation group. Disease progression was compared in 3 of the 6 studies. 2 studies reported minimal disease progression (0-3.5%) and no significant difference between operation and observation group. Perioperative deaths were rare (0-3%), but complications were common (33-46%). None of the 46 patients who crossed over form observation to operation group had disease recurrence after resection. CONCLUSION: Small NF-PNETs without distant metastasis, lymph node metastasis and local invasion on imaging studies can be observed without increase in death and disease progression.