Progress In Surgical Treatment And Prognostic Analysis Of Non-functioning Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors(PNETs)are rare,heterogeneous pancreatic tumors with different biological behaviors,clinical features,pathologic features and outcomes.In recent decades,with the rapid development and widely use of imaging technology around the world,the incidence of pancreatic neuroendocrine tumors is increasing,including asymptomatic,small non-functioning pancreatic neuroendocrine tumors(NF-PNETs).However,for this type of non-functioning pancreatic tumors,especially the imaging examination indicated the maximum diameter of the tumor is less than 2cm,and without any clinical symptoms,its diagnosis,pathological features,treatment and prognostic factors are still in great controversy.Based on this background,we retrospectively analyzed the general condition,pathologic features,surgical treatment and prognostic factors of patients with NF-PNETs in our center,which were designed to provide clinical basis of diagnosis,treatment and management of NF-PNETs,and to provide experience for the promotion of a multi-center,large sample of clinical randomized controlled trials(RCT),the development of guidelines and the precise treatment of the tumors.Objective:To explore the progress of surgical treatment of NF-PNETs,and to analyze the risk factors of recurrence、metastasis and long-term survival in patients with NF-PNETs.Methods:Patients with NF-PNETs who were managed surgically or by surveillance between June 2007 and December 2013 were retrospectively studied.The choice of surgery or surveillance was based entirely on the patient’s desire.53 patients were included into this study,five of the patients with small tumor were followed up through imaging surveillance and 48 patients underwent surgical treatment.The surgical patients were divided into symptomatic and asymptomatic groups.According to different surgical methods,patients were divided into pancreatic parenchymal pancreatic resection group(PPR)and formal pancreatic resection group.The general condition,surgical procedure,pathological grade,survival time and prognostic factors were analyzed among different subgroups.Data were analyzed by SPSS 19.0 statistical analysis,with a P<0.05 for the difference was statistically significant.Results:Of the 53 patients with NF-PNETs,48(90%)were treated surgically.25 patients(47%)were symptomatic patients,23(43%)asymptomatic,and five(10%)detected by surveillance.Among the latter group,one patient suffered from tumor progression and four had stable disease.When compared with symptomatic NF-PNETs,asymptomatic NF-PNETs showed lower pathology grades(P=0.006),better 3-year cumulative progression-free survival and overall survival after surgical treatment.Parenchyma-preserving resection was associated with a higher risk of pancreatic fistula(71 vs.17%,P =0.007).A positive lymph node status(P=0.003)and perineural or vascular invasion(P=0.01)were significant predictors of tumor recurrence or metastasis.Patients with grade G3 disease(P =0.005)or a tumor size>4 cm(P=0.019)had poor prognosis.Conclusion:Compared with symptomatic NF-PNETs,patients with asymptomatic NF-PNETs had a lower degree of malignancy and a better prognosis.Parenchyma preserved pancreatic resection is safe and effective for patients with small tumor size and without lymphvascular invasion.Positive regional lymph node,peripheral vascular invasion are independent risk factors for tumor recurrence and metastasis.Pathological grading G3,tumor greater than 4cm are independent risk factors for long-term survival of patients.The safety of follow-up surveillance of small,asymptomatic NF-PNETs patients needs to be conformed through multi-center,large sample size studies.