Background: Postpancreatectomy hemorrhage is a potentially lethal complication after pancreatic resection. The objective of this systematic review is to provide insight in the current status of incidence, detection, management and clinical outcomes of late postpancreatectomy hemorrhage. Methods: A systematic search was conducted on the literature from February 2007 to July 2018 in PubMed, Embase and the Cochrane library. Included were clinical studies with clinical outcomes on late postpancreatectomy hemorrhage defined according to the International Study Group of Pancreatic Surgery definition (i.e. occurring >24 h after pancreatic resection).Results: A total of 14 studies on 467 patients with late postpancreatectomy hemorrhage were included.The incidence of late postpancreatectomy hemorrhage ranged from 3% to 16% (weighted mean: 5%).Seventy-four patients received conservative treatment; 252 patients underwent primary endovascular intervention; 82 patients underwent primary relaparotomy; 56 patients underwent primary endoscopic intervention; and three patients died before any intervention could be performed. CT-scan and diagnostic angiography were able to identify the source of hemorrhage in 67% (66/98) and 69% (114/166) of patients, respectively. The most frequent origin of the hemorrhage was the gastroduodenal artery stump (79/275; 29%), followed by the common hepatic artery (51/275; 19%) and splenic artery (32/275; 12%).Overall mortality was 21% (98/464 patients; range 0%-38%). Mortality was lower after primary interventional angiography as compared to primary relaparotomy (16% vs 37% respectively). Conclusions:This systematic review provides a comprehensive overview of the current literature for severe late postpancreatectomy hemorrhages. CT-scan and diagnostic angiography are equally sensitive in detecting the bleeding source. Interventional angiography appears to be associated to lower mortality as compared to relaparotomy and endoscopy as first intervention for postpancreatectomy hemorrhage.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy characterized by extensive local invasion and systemic spread. In this study, we employed a three-dimensional organoid model of human pancreatic cancer to characterize the molecular alterations critical for invasion. Time-lapse microscopy was used to observe invasion in organoids from 25 surgically resected human PDAC samples in collagen I. Subsequent lentiviral modification and small-molecule inhibitors were used to investigate the molecular programs underlying invasion in PDAC organoids. When cultured in collagen I, PDAC organoids exhibited two distinct, morphologically defined invasive phenotypes, mesenchymal and collective. Each individual PDAC gave rise to organoids with a predominant phenotype, and PDAC that generated organoids with predominantly mesenchymal invasion showed a worse prognosis. Collective invasion predominated in organoids from cancers with somatic mutations in the driver gene SMAD4 (or its signaling partner TGFBR2). Reexpression of SMAD4 abrogated the col-lective invasion phenotype in SMAD4-mutant PDAC organoids, indicating that SMAD4 loss is required for collective invasion in PDAC organoids. Surprisingly, invasion in passaged SMAD4mutant PDAC organoids required exogenous TGFb, suggesting that invasion in SMAD4-mutant organoids is mediated through noncanonical TGFb signaling. The Rho-like GTPases RAC1 and CDC42 acted as potential mediators of TGFb-stimulated invasion in SMAD4-mutant PDAC organoids, as inhibition of these GTPases suppressed collective invasion in our model. These data suggest that PDAC utilizes different invasion programs depending on SMAD4 status, with collective invasion uniquely present in PDAC with SMAD4 loss.Significance: Organoid models of PDAC highlight the importance of SMAD4 loss in invasion, demonstrating that invasion programs in SMAD4-mutant and SMAD4 wild-type tumors are different in both morphology and molecular mechanism.

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