***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Purpose Pancreatoduodenectomy ( PD ) with superior mesenteric/portal venous resection ( PVR ) for pancreatic ductal adenocarcinoma ( PDAC ) is performed routinely in case of tumor adhesion to the superior mesenteric or portal vein . True histopathological portal vein invasion ( PVI ) is found in a subgroup of patients . Even though this procedure has become routine in most centers for pancreatic surgery , data on prognostic factors in this situation is limited . The aim of this study was to identify prognostic factors after PD with PVR for PDAC . Methods Retrospective analysis was performed on the basis of a prospect ively maintained data base , and paraffin-embedded formalin-fixed tissue slides stained for hematoxylin-eosin were re-evaluated by two independent pathologists . Statistical analysis was conducted using MedCalc software . Results From 2001 to 2012 , 86 cases of PD with PVR for PDAC with long-term follow-up and sufficient tissue for re- assessment were identified . Histopathological re- review disclosed PVI in 39 resection specimens and adhesion without infiltration in 47 . Overall median survival in all patients was 22 months . Patients with PVI versus no PVI showed comparable baseline demographic and st and ard histopathological parameters ; however , PVI was associated with microscopic hemangiosis ( p = 0.001 ) and positive margin status ( p = 0.001 ) . Median survival in patients with PVI was 14 months versus 25 months in patients without PVI ( p = 0.042 ) . Only lymph node ratio and PVI were independent predictors of survival after resection . Conclusion The only independent factors influencing overall survival after PD with PVR for PDAC were lymph node ratio and PVI . PVI might indicate aggressive tumor biology , but the available data remains controversial HYPOTHESIS An aggressive strategy that includes extended lymphadenectomy and vein resection may improve the results of surgical treatment of pancreatic head cancer . DESIGN Nonr and omized control trial . SETTING Tertiary care referral center . PATIENTS The study included 149 consecutive patients undergoing macroscopically curative resection for periampullary adenocarcinoma from January 1 , 1988 , to December 31 , 1998 . INTERVENTIONS A st and ard resection was performed in 122 cases ; an extended lymphadenectomy in 37 . Twenty-four patients underwent venous resection . MAIN OUTCOME MEASURES Data on surgical mortality , morbidity , and postoperative outcome , pathological findings , and long-term survival were analyzed . RESULTS In-hospital and 60-day operative mortality was 5.4 % . Morbidity was 37.5 % . Mortality , morbidity , and postoperative stay were nonsignificantly modified by extended lymphadenectomy or venous resection . Extended resection permitted the identification of a significantly higher percentage of nodal metastases beyond the peripancreatic node groups . In patients undergoing vein resection , a significantly higher rate of positive retroperitoneal margin was found . In the 100 patients with ductal adenocarcinoma , the median overall survival and the 5-year actuarial survival rate were 15 months and 8.4 % , respectively . A trend toward a better survival was observed in the first 2 years after operation in the extended resection group compared with the st and ard resection group . Nodal status was the most powerful predictor of overall survival by multivariate analysis . CONCLUSIONS Extended lymphadenectomy and vein resection did not adversely affect postoperative mortality and morbidity . Patients who required a vein resection were less likely to receive a microscopically curative pancreatectomy . Extended resection permitted better pathological staging and was associated with an early advantage in survival , but long-term survival was possible only in patients with favorable prognostic factors INTRODUCTION Complete tumor extirpation ( R0 resection ) remains the best possibility for long-term survival in patients with pancreatic adenocarcinoma . Unfortunately , approximately 80 % of patients are not amenable to resection at diagnosis either because of metastatic ( 40 % ) or locally advanced disease ( 40 % ) . Recent reports of irreversible  electroporation  ( IRE ) , a high-voltage , short-pulse , cellular energy ablation device , have shown the modality to be safe and potentially beneficial to prognosis . IRE to augment/accentuate the margin during pancreatic resection for certain locally advanced pancreatic cancers has not been reported . METHODS Patients with locally advanced/borderline resectable pancreatic cancer who underwent pancreatectomy with margin accentuation with IRE were followed in a prospect i ve , institutional review board-approved data base from July 2010 to January 2013 . Data regarding local recurrence , margin status , and survival were evaluated . RESULTS A total of 48 patients with locally advanced pancreatic/borderline cancers underwent pancreatectomy , including pancreatoduodenectomy ( 58 % ) , subtotal pancreatectomy ( 35 % ) , distal pancreatectomy ( 4 % ) , and total pancreatectomy ( 4 % ) , with IRE margin accentuation of the superior mesenteric artery and /or the anterior margin of the aorta . Most patients had undergone induction therapy with 33 patients ( 69 % ) receiving chemoradiation therapy and 18 patients chemotherapy for a median of 6 months ( range , 4 - 13 ) before resection . A majority ( 54 % ) required vascular resection . A total of 9 patients ( 19 % ) , sustained 21 complications with a median grade of 2 ( range , 1 - 3 ) , with a median duration of stay of 7 days ( range , 4 - 58 ) . With median follow-up of 24 months , 3 ( 6 % ) have local recurrence , with a median survival of 22.4 months . CONCLUSION Simultaneous intraoperative IRE and pancreatectomy can provide an adjunct to resection in patients with locally advanced disease . Long-term follow-up has demonstrated a small local recurrence rate that is lower than expected . Continued optimization in multimodality therapy and consideration of appropriate patients could translate into a larger subset that could be treated effectively 
    Output:
    
Conclusions Histopathologic tumor invasion of the SMV/PV is associated with more aggressive biologic behavior and could be used as an indicator of poor prognosis after PDAC resection