Search

In this work, we investigate the potential of combining Artificial Intelligence (AI) tree-search algorithms with the algorithms of combinatorial game theory to provide more efficient strategies for playing sum games based on subgame types. Two new approximate strategies are developed and tested using a specified game model. Both strategies achieve higher performance than approximate strategies previously proposed in literature without being computationally more expensive.

Combinatorial games of the form {{A|B}|{C|D}} can be classified as either left excitable, right excitable, or equitable [2]. Several approximate strategies for playing sums of games of this form have been proposed in the literature [2,3,4]. In this work we propose a new approach for evaluating the different strategies based on the types of the subgames participating in a sum game. While previous comparisons [3,4] were only able to rank the strategies according to their average performance in a large number of randomly generated games, our evaluation is able to pinpoint the strengths and weaknesses of each strategy. We show that none of the strategies can be considered the best in an absolute sense. Therefore we recommend the development of type-based approximate strategies with enhanced performance.

Objectives Pancreaticoduodenectomy (PD) is associated with a high risk of postoperative complications and mortality. The aim of this study was to compare postoperative morbidity after PD in patients undergoing resections for pancreatic neuroendocrine neoplasms (PanNENs) with patients undergoing the same resection for pancreatic ductal adenocarcinoma (PDAC). Methods Data of 566 patients from 3 European tertiary referral centers between 1998 and 2014 were considered. Results Overall, 566 patients (179 with PanNENs, 387 with PDAC) who underwent PD were analyzed. Patients with PanNENs were significantly younger (56 vs 64 years, P < 0.0001). The consistency of the pancreas was soft in 147 patients (82%) with PanNENs and in 162 patients (42%) with PDAC (P < 0.0001). Patients in the PanNENs group had a significantly higher rate of pancreatic fistula (P < 0.0001), bile leak (P = 0.004), abdominal collection (P = 0.017), and development of sepsis (P = 0.042). No differences in terms of overall postoperative complications, median length of stay, and in-hospital mortality were found. On multivariate analysis sex (male), PanNENs indication, blood transfusion, and a soft pancreatic texture were independent predictors of pancreatic fistula after PD. Conclusions Pancreaticoduodenectomy for PanNENs is associated with higher rate of surgical-specific postoperative complications than those for PDAC.

Nonfunctioning pancreatic neuroendocrine tumors (NF-PanNETs) are often indolent neoplasms without lymph node (LN) metastasis at diagnosis. Therefore, in patients with low risk of LN metastasis, the extent of surgery and lymphadenectomy could be limited and follow-up adjusted to the very low risk of relapse.To construct a predicting model to assess the risk of pN+ prior to surgical resection for NF-PanNETs using preoperative retrievable variables.Retrospective review using multiple logistic regression analysis to construct predictive model of pN+ based on preoperatively available data.The combined prospective databases of the Surgical Departments of the University of Verona, Verona, Italy, and Beaujon Hospital, Clichy, France, were queried for clinical and pathological data.All patients with resected (R0 or R1), pathologically confirmed NF-PanNETs between January 1, 1993 and December 31, 2009.Risk of lymph node metastases in patients with pancreatic neuroendocrine tumors.Among 181 patients, nodal metastases were reported in 55 patients (30%) and were associated with decreased 5-year disease-free survival (70% vs 97%, P .001). Multivariable analysis showed that independent factors associated with nodal metastasis were radiological nodal status (rN) (odds ratio [OR], 5.58; P .001) and tumor grade (NET-G2 vs NET-G1: OR, 4.87; P .001) (first model). When the tumor grade was excluded, rN (OR, 4.73; P = .001) and radiological tumor size larger than 4 cm (OR, 2.67; P = .03) were independent predictors of nodal metastasis (second model). The area under the receiver operating characteristic curve for the first and second models were 80% and 74%, respectively.Patients with NF-PanNET-G1 have a very low risk of pN+ in the absence of radiological signs of node involvement. When preoperative grading assessment is not achieved, the radiological size of the lesion is a powerful alternative predictor of pN+. The risk of pathological nodal involvement in patients with NF-PanNETs can be accurately estimated by a clinical predictive model.