Moment Closure - A Brief Review

Moment closure methods appear in myriad scientific disciplines in the modelling of complex systems. The goal is to achieve a closed form of a large, usually even infinite, set of coupled differential (or difference) equations. Each equation describes the evolution of one "moment", a suitable coarse-grained quantity computable from the full state space. If the system is too large for analytical and/or numerical methods, then one aims to reduce it by finding a moment closure relation expressing "higher-order moments" in terms of "lower-order moments". In this brief review, we focus on highlighting how moment closure methods occur in different contexts. We also conjecture via a geometric explanation why it has been difficult to rigorously justify many moment closure approximations although they work very well in practice.Comment: short survey paper (max 20 pages) for a broad audience in mathematics, physics, chemistry and quantitative biolog

Cap-assisted forward-viewing endoscopy to visualize the ampulla of Vater and the duodenum in patients with familial adenomatous polyposis

Background and study aims Guidelines recommend surveillance endoscopy with both forward- and side-viewing endoscopes to identify duodenal and ampullary adenomas in patients with familial adenomatous polyposis (FAP). We hypothesized that both the duodenum and the ampulla of Vater can be completely visualized during cap-assisted forward-viewing endoscopy. Patients and methods A total of 40 patients with FAP underwent forward-viewing endoscopy with a short cap attached to the tip of the gastroscope, with the aim of visualizing both the duodenum and the ampulla of Vater. If unsuccessful, the procedure was followed by a side-viewing endoscopy. Adverse events were reported. Results The duodenum, including the ampulla of Vater, was completely visualized using the cap in 38/40 patients (95.0%). The ampulla could not be visualized using the cap in two patients, both of whom underwent additional side-viewing endoscopy, which was successful. No adverse events occurred. Conclusions This study showed that cap-assisted endoscopy can be used effectively and safely to visualize both the duodenum and the ampulla of Vater in patients with FAP. This practice might reduce burden, time, and costs of an additional side-viewing endoscop

Duodenal Adenomas in Patients With Multiple Colorectal Adenomas Without Germline APC or MUTYH Mutations

BACKGROUND: Patients with genetic adenomatous polyposis syndromes have an increased risk for duodenal cancer, and clear surveillance recommendations exist for this group. However, limited data are available on the duodenal phenotype of patients with multiple colorectal adenomas (10-99) without a germline APC or MUTYH mutation. OBJECTIVE: We aimed to assess the frequency, extent, and progression of duodenal adenomas in patients with multiple colorectal adenomas without a germline APC or MUTYH mutation. DESIGN: This was an historical cohort study. SETTINGS: This study was undertaken at 2 polyposis registries: the Academic Medical Center in the Netherlands, and St. Mark's Hospital in the United Kingdom. PATIENTS: We collected data on all patients with 10 to 99 colorectal adenomas and absent APC and MUTYH mutations, who underwent 1 esophagogastroduodenoscopy. MAIN OUTCOME MEASURES: The frequency, extent, and progression of duodenal adenomas were measured. Demographic and endoscopic data were collected, described, and compared between patients with and without duodenal adenomas. RESULTS: Eighty-three patients were identified, of which 8 (9.6%) had duodenal adenomas, detected at a median of 58 years (range, 45-75 y). Duodenal adenomas were detected in 6 of 8 patients at first esophagogastroduodenoscopy. At diagnosis, all 8 patients had Spigelman stage I or II disease. Two of 5 patients with duodenal adenomas who underwent follow-up esophagogastroduodenoscopies increased to stage III disease. The other 3 remained stable. No one developed duodenal cancer. No differences in demographic and endoscopic data were found between patients with and without duodenal adenomas. LIMITATIONS: This study was limited by its retrospective design, selection bias, and small sample size. CONCLUSIONS: Duodenal adenomas are found in a minority of patients with multiple colorectal adenomas without a germline APC or MUTYH mutation, at an average age of 58 years, and, at diagnosis, disease severity is mild. These results are a first step in unraveling the duodenal phenotype of these patients, which is needed to provide appropriate upper GI screening and surveillance recommendations. See Video Abstract at http://links.lww.com/DCR/A35

Preferences for genetic testing for colorectal cancer within a population-based screening program: a discrete choice experiment

This study explored individuals' preferences for genetic testing for colorectal cancer (CRC) in a screening situation and their willingness to participate in genetic testing for Lynch syndrome, familial adenomatous polyposis (FAP), and familial colorectal cancer (FCC). For that purpose, 532 respondents aged 55-65 years completed a Discrete Choice Experiment. Using panel latent class models, the preferences for two screening situation characteristics (the probability of being genetically predisposed and the probability of developing CRC) and screening test characteristics (the frequency of preventive colonoscopies and CRC survival) were estimated. Based on these preferences, respondents' willingness to participate in the three screening initiatives was estimated. Lower-educated respondents and respondents who express serious anxiety and worries found colonoscopy frequency and the probability of developing CRC relatively more important and survival relatively less important compared with higher-educated respondents and respondents who express no anxiety and worries. These differences in preferences resulted in opposite preferences for participation in FCC and FAP screening. In conclusion, the general population is willing to participate in genetic screening for CRC. If individuals are suspected of genetic or familial CRC, they should at least be informed about their increased risk of being genetically predisposed and about the importance of participating in all preventive follow-up colonoscopies in order to maximize surviva

Preferences for genetic testing for colorectal cancer within a population-based screening program: a discrete choice experiment

This study explored individuals' preferences for genetic testing for colorectal cancer (CRC) in a screening situation and their willingness to participate in genetic testing for Lynch syndrome, familial adenomatous polyposis (FAP), and familial colorectal cancer (FCC). For that purpose, 532 respondents aged 55-65 years completed a Discrete Choice Experiment. Using panel latent class models, the preferences for two screening situation characteristics (the probability of being genetically predisposed and the probability of developing CRC) and screening test characteristics (the frequency of preventive colonoscopies and CRC survival) were estimated. Based on these preferences, respondents' willingness to participate in the three screening initiatives was estimated. Lower-educated respondents and respondents who express serious anxiety and worries found colonoscopy frequency and the probability of developing CRC relatively more important and survival relatively less important compared with higher-educated respondents and respondents who express no anxiety and worries. These differences in preferences resulted in opposite preferences for participation in FCC and FAP screening. In conclusion, the general population is willing to participate in genetic screening for CRC. If individuals are suspected of genetic or familial CRC, they should at least be informed about their increased risk of being genetically predisposed and about the importance of participating in all preventive follow-up colonoscopies in order to maximize survival

How psychological distance of a study sample in discrete choice experiments affects preference measurement : a colorectal cancer screening case study

Purpose: The purpose of this study was to investigate to what extent the outcomes of a discrete choice experiment (DCE) differ based on respondents' psychological distance to the decision at hand. Methods: A DCE questionnaire regarding individuals' preferences for genetic screening for colorectal cancer (CRC) within the Dutch national CRC screening program was created. The DCE contained nine D-efficient designed choice tasks and was distributed among two populations that differ in their psychological distance to the decision at hand: 1) a representative sample of the Dutch general population aged 55-65 years, and 2) a sample of Dutch individuals who attended an information appointment regarding colonoscopies following the detection of blood in their stool sample in the CRC screening program. The DCE consisted of four attributes related to the decision whether to participate in genetic screening for CRC: 1) risk of being genetically predisposed, 2) risk of developing CRC, 3) frequency of follow-up colonoscopies, and 4) survival. Direct attribute ranking, dominant decision-making behavior, and relative importance scores (based on panel MIXL) were compared between the two populations. Attribute level estimates were compared with the Swait and Louviere test. Results: The proportion of respondents who both ranked survival as the most important attribute, and showed dominant decision-making behavior for this attribute, was significantly higher in the screened population compared to the general population. The relative importance scores of the attributes significantly differed between populations. Finally, the Swait and Louviere test also revealed significant differences in attribute level estimates in both the populations. Conclusion: The study outcomes differed between populations depending on their psychological distance to the decision. This study shows the importance of adequate sample selection; therefore, it is advocated to increase attention to study sample selection and reporting in DCE studies

Endoscopic management of duodenal adenomas in patients with familial adenomatous polyposis

Background and Aims: Almost all patients with familial adenomatous polyposis (FAP) develop duodenal adenomas, with a 4% to 18% risk of progression into duodenal cancer. Prophylactic endoscopic resection of duodenal adenomas may prevent cancer and is considered safer than surgical alternatives; however, data are limited. Therefore, the aim of this study was to assess safety and effectiveness of endoscopic duodenal interventions in patients with FAP. Methods: We performed a historical cohort study including patients with FAP who underwent an endoscopic duodenal intervention between 2002 and 2018. Safety was defined as adverse event rate per intervention and effectiveness as duodenal surgery–free and duodenal cancer–free survival. Change in Spigelman stage was assessed as a secondary outcome. Results: In 68 endoscopy sessions, 139 duodenal polypectomies were performed in 49 patients (20 men; median age, 43). Twenty-nine patients (14 men; median age, 49) underwent a papillectomy. After polypectomy, 9 (13%) bleedings and 1 (2%) perforation occurred, all managed endoscopically. Six (21%) bleedings (endoscopically managed), 4 (14%) cases of pancreatitis, and 1 (3%) perforation (conservatively treated) occurred after papillectomy. Duodenal surgery–free survival was 74% at 89 months after polypectomy and 71% at 71 months after papillectomy; no duodenal cancers were observed. After a median of 18 months (interquartile range, 10-40; range, 3-121) after polypectomy, Spigelman stages were significantly lower (P <.01). Conclusions: In our FAP patients, prophylactic duodenal polypectomies were relatively safe. Papillectomies showed substantial adverse events, suggesting its benefits and risk should be carefully weighted. Both were effective, however, because surgical interventions were limited and none developed duodenal cancer

Sirolimus for the treatment of polyposis of the rectal remnant and ileal pouch in four patients with familial adenomatous polyposis: A pilot study

Objective After prophylactic colectomy, adenomas continue to develop in the remaining intestine of patients with familial adenomatous polyposis (FAP). There is a lack of standard clinical recommendation for chemoprevention in patients with FAP. Because of promising in vivo studies, the aim of this pilot study was to investigate the safety of sirolimus and its effect on progression of intestinal adenomas. Design Patients with FAP with InSiGHT Polyposis Staging System 3 of the retained rectum or pouch received sirolimus for 6 months, dosed at plasma concentration levels of 5-8 μg/L. Primary outcomes were safety and change in marked polyp size. Secondary outcomes were change in number of polyps and effect on proliferation and apoptosis assessed by immunohistochemistry. Results Each of the included four patients reported 4 to 18 adverse events (toxicity grades 1-3). One patient prematurely terminated the study because of adverse events. Marked polyp size decreased in 16 (80%)/20 and remained the same in 4 (20%)/20 patients. The number of polyps decreased in all patients (MD -25.75, p=0.13). Three out of four patients showed substantial induction of apoptosis or inhibition of proliferation. Conclusion Six months of sirolimus treatment in four patients with FAP showed promising effects especially on the number of polyps in the rectal remnant and ileal pouch, although at the cost of numerous adverse events. Trial registration number ClinicalTrials.gov ID NCT03095703

Induction of p53-Specific Immunity by a p53 Synthetic Long Peptide Vaccine in Patients Treated for Metastatic Colorectal Cancer

Purpose: The tumor-associated self-antigen p53 is commonly overexpressed in cancer, including colorectal cancer, and can serve as a target for immunotherapy. The safety and immunogenicity of a p53 synthetic long peptide (p53-SLP) vaccine were investigated in patients treated for metastatic colorectal cancer. Experimental Design: Ten patients were vaccinated twice with a set of 10 overlapping p53-SLP in a phase I/II trial. Both the safety and the breadth, magnitude, and polarization of vaccine-induced p53-specific T cells was evaluated in blood samples drawn before and after vaccination by IFN-gamma enzyme-linked immunospot, proliferation, cytokine secretion, and multiparameter flow cytometry. The migratory capacity of p53-specific T cells was evaluated by assessing their presence in a biopsy of the second vaccination site. Results: Toxicity was limited to grade 1/2, mostly at the vaccination site. p53-specific T-cell responses were induced in 9 of 10 colorectal cancer patients as measured by IFN-gamma enzyme-linked immunospot, proliferation, and cytokine bead array. In 6 of 9 tested patients, p53-specific T-cell reactivity persisted at least 6 months. Furthermore, p53-specific T cells isolated from the vaccination site were characterized as CD4(+) T cells producing both T-helper types 1 and 2 cytokines on stimulation with p53 peptide and p53 protein. Multiparameter flow cytometry revealed that only a minor population of the p53-specific CD4(+) T cells was optimally polarized. Conclusions: The p53-SLP vaccine is safe and capable to induce p53-specific T-cell responses in patients treated for colorectal cancer. New trials should focus on improving the polarization of the p53-SLP vaccine-induced T-cell response