Diabetes mellitus increases the risk of colorectal neoplasia: An updated meta-analysis

Exogenous Insulin Therapy Is Associated with the Risk of Advanced Colorectal Adenoma in Patients with Diabetes Mellitus

BACKGROUND/AIMS

Exogenous insulin therapy increases systemic exposure to insulin which may promote the development of colorectal neoplasia. We sought to evaluate the association between exogenous insulin therapy and the incidence of advanced adenoma in type 2 diabetes mellitus.

METHODS

A retrospective cohort study was conducted from January 1, 2007, to January 1, 2018, in a regional health system serving the United States Philadelphia metropolitan area, Central New Jersey, and South Central Pennsylvania. Study patients consisted of a random sample of patients with type 2 diabetes mellitus aged 40-80 years who had undergone two rounds of colonoscopy examinations. The exposure was cumulative duration of insulin therapy (i.e., no use, 1-365 days and > 365 days). The outcome was time to incident advanced adenoma.

RESULTS

Of the 975 eligible patients, 184 patients accumulated > 365 days of insulin therapy before the follow-up colonoscopy. The mean (standard deviation) duration between the two rounds of colonoscopy examination was 5.1 (2.9) years among the insulin users and 5.3 (3.9) years among non-users. Compared to no insulin exposure, receiving > 365 days of insulin therapy was associated with an increased incidence of advanced adenoma (adjusted hazard ratio [aHR] 4.84, 95% confidence interval [CI] 2.82-8.30), right-sided advanced adenoma (aHR 5.48, 95% CI 2.90-10.35), and 3 or more adenomas (aHR 2.61, 95% CI 1.46-4.69) at the follow-up colonoscopy examination.

CONCLUSION

Insulin therapy is associated with an increased risk of advanced adenoma and may serve as a novel risk-stratification factor to enhance the efficiency of existing colorectal cancer screening and surveillance programs.

Predicting Risk of Colorectal Cancer After Adenoma Removal in a Large Community-Based Setting

INTRODUCTION

Colonoscopy surveillance guidelines categorize individuals as high or low risk for future colorectal cancer (CRC) based primarily on their prior polyp characteristics, but this approach is imprecise, and consideration of other risk factors may improve postpolypectomy risk stratification.

METHODS

Among patients who underwent a baseline colonoscopy with removal of a conventional adenoma in 2004-2016, we compared the performance for postpolypectomy CRC risk prediction (through 2020) of a comprehensive model featuring patient age, diabetes diagnosis, and baseline colonoscopy indication and prior polyp findings (i.e., adenoma with advanced histology, polyp size ≥10 mm, and sessile serrated adenoma or traditional serrated adenoma) with a polyp model featuring only polyp findings. Models were developed using Cox regression. Performance was assessed using area under the receiver operating characteristic curve (AUC) and calibration by the Hosmer-Lemeshow goodness-of-fit test.

RESULTS

Among 95,001 patients randomly divided 70:30 into model development (n = 66,500) and internal validation cohorts (n = 28,501), 495 CRC were subsequently diagnosed; 354 in the development cohort and 141 in the validation cohort. Models demonstrated adequate calibration, and the comprehensive model demonstrated superior predictive performance to the polyp model in the development cohort (AUC 0.71, 95% confidence interval [CI] 0.68-0.74 vs AUC 0.61, 95% CI 0.58-0.64, respectively) and validation cohort (AUC 0.70, 95% CI 0.65-0.75 vs AUC 0.62, 95% CI 0.57-0.67, respectively).

DISCUSSION

A comprehensive CRC risk prediction model featuring patient age, diabetes diagnosis, and baseline colonoscopy indication and polyp findings was more accurate at predicting postpolypectomy CRC diagnosis than a model based on polyp findings alone.

Type 2 Diabetes and Colorectal Cancer Risk

Importance

Type 2 diabetes and colorectal cancer (CRC) disproportionately burden indviduals of low socioeconomic status and African American race. Although diabetes is an emerging CRC risk factor, associations between diabetes and CRC in these populations are understudied.

Objective

To determine if diabetes is associated with CRC risk in a cohort representing understudied populations.

Design, Setting, and Participants

This cohort study uses data from the prospective Southern Community Cohort Study in the US, which recruited from 2002 to 2009 and completed 3 follow-up surveys by 2018. Of about 85 000 participants, 86% enrolled at community health centers, while 14% were enrolled via mail or telephone from the same 12 recruitment states. Participants with less than 2 years of follow-up, previous cancer diagnosis (excluding nonmelanoma skin cancer) at enrollment, missing enrollment diabetes status, diabetes diagnosis before age 30, and without diabetes at enrollment with no follow-up participation were excluded. Data were analyzed from January to September 2023.

Exposures

Physician-diagnosed diabetes and age at diabetes diagnosis were self-reported via survey at enrollment and 3 follow-ups.

Main Outcomes and Measures

Diabetes diagnosis was hypothesized to be positively associated with CRC risk before analysis. Incident CRC was assessed via state cancer registry and National Death Index linkage. Hazard ratios and 95% CIs were obtained via Cox proportional hazard models, using time-varying diabetes exposure.

Results

Among 54 597 participants, the median (IQR) enrollment age was 51 (46-58) years, 34 786 (64%) were female, 36 170 (66%) were African American, and 28 792 (53%) had income less than $15 000 per year. In total, 289 of 25 992 participants with diabetes developed CRC, vs 197 of 28 605 participants without diabetes. Diabetes was associated with increased CRC risk (hazard ratio [HR], 1.47; 95% CI, 1.21-1.79). Greater associations were observed among participants without colonoscopy screening (HR, 2.07; 95% CI, 1.16-3.67) and with smoking history (HR, 1.62; 95% CI, 1.14-2.31), potentially due to cancer screening differences. Greater associations were also observed for participants with recent diabetes diagnoses (diabetes duration <5 years compared with 5-10 years; HR, 2.55; 95% CI, 1.77-3.67), possibly due to recent screening.

Conclusions and Relevance

In this study where the majority of participants were African American with low socioeconomic status, diabetes was associated with elevated CRC risk, suggesting that diabetes prevention and control may reduce CRC disparities. The association was attenuated for those who completed colonoscopies, highlighting how adverse effects of diabetes-related metabolic dysregulation may be disrupted by preventative screening.

The impact of diabetes on cancer detection during the prevalence round of a national screening program for colorectal cancer

AIMS

Diabetes is associated with a higher risk of colorectal cancer (CRC) and inferior survival after CRC. Screening may enable the early detection of CRC. We aimed to assess the impact of diabetes on cancer detection and disease stage during the prevalence round of a national CRC screening program.

METHODS

We performed a register-based cohort study based on the randomized procedure for inviting Danish residents aged 50-74 years to the prevalence round of national CRC screening program in 2014-2017. By comparing the random half of the population who had been invited by 1 May 2016 with the not yet invited half, the effect of screening was assessed by the detection of CRC and disease stage among individuals with and without diabetes. Further, the impact of diabetes on the screening participation rate was calculated.

RESULTS

By randomisation, 504,673 individuals had been invited to the CRC screening by 1 May 2016, and 549,359 individuals had not yet been invited. The diabetes prevalence was 10% in both groups. When comparing those not yet invited to those invited, the effect of screening on the number of detected cancers per 100,000 individuals was higher in those with diabetes (from 207 to 494 cancers) than in those without diabetes (from 147 to 364 cancers), and screening resulted in overall higher proportions of stage I cancer. Among those invited to screening, the participation rate was 9.1% lower (95% CI: 8.7%-9.5%) in individuals with versus without diabetes.

CONCLUSIONS

Despite a lower participation rate, the effect of CRC screening was higher in individuals with diabetes.

Diabetes is associated with high risk of severe adverse events during chemotherapy for cancer patients: A single-center study

Diabetes mellitus (DM) is a common comorbidity among cancer patients, but its impact on chemotherapy tolerance has not been widely studied. We aimed to compare the occurrence of severe grade 3/4 adverse events (G3/4 AEs) within 90 days of starting chemotherapy between patients with and without diabetes. We conducted a retrospective single-center study in Lille University Hospital Oncology Department, France. Patients who received the first cycle of chemotherapy for gastrointestinal, gynecological or cancer of unknown primary source between 1 May 2013 and 1 May 2016, were included. Overall, 609 patients were enrolled: 490 patients without diabetes (80.5%) and 119 patients with diabetes (19.5%). Within 90 days of starting chemotherapy, patients with diabetes had a significantly higher occurrence of AEs G3/4 compared to those with no diabetes (multivariate odds ratio [OR]: 1.57 [1.02-2.42], P = .04). More frequent G3/4 AEs in patients with diabetes were infection (26%), hematological disorders (13%), endocrine disorders (13%) and deterioration of the general condition (13%). In the year following the beginning of chemotherapy, patients with diabetes were twice as likely to be hospitalized as those without diabetes (univariate OR: 2.1 [1.40-3.15], P = .0003). After multivariate adjustment, diabetes was no longer significantly associated with the risk of hospitalization (P = .051). There were no differences between patients with and without diabetes regarding dose reduction and chemotherapy treatment delays (P = .61 and P = .30, respectively). Our study suggests the need for better consideration of DM in the personalized care plan to improve chemotherapy tolerance and quality of life of patients with DM.

Adenoma Detection Rate and Clinical Characteristics Influence Advanced Neoplasia Risk After Colorectal Polypectomy

BACKGROUND AND AIMS

Postpolypectomy risk stratification for subsequent metachronous advanced neoplasia (MAN) is imprecise and does not account for colonoscopist adenoma detection rate (ADR). Our aim was to assess association of ADR with MAN and create a prediction model for postpolypectomy risk stratification incorporating ADR and other factors.

METHODS

We conducted a retrospective cohort study of individuals with baseline polypectomy and subsequent surveillance colonoscopy from 2004 to 2016 within the U.S. Department of Veterans Affairs (VA). Clinical factors, polyp findings, and baseline colonoscopist ADR were considered for the model. Model performance (sensitivity, specificity, and area under the curve) for identifying individuals with MAN was compared with 2020 U.S. Multi-Society Task Force on Colorectal Cancer (USMSTF) surveillance recommendations.

RESULTS

A total of 30,897 individuals were randomly assigned 2:1 into independent model training and validation sets. Increasing age, male sex, diabetes, current smoking, adenoma number, polyp location, adenoma ≥10 mm or with tubulovillous/villous features, and decreasing colonoscopist ADR were independently associated with MAN. A range of 1.48- to 1.66-fold increased risk for MAN was observed for ADR in the lowest 3 quintiles (ADR <19.7%-39.3%) vs the highest quintile (ADR >47.0%). When the final model selected based on the training set was applied to the validation set, improved sensitivity and specificity over 2020 USMSTF risk stratification were achieved (P = .001), with an area under the curve of 0.62 (95% confidence interval, 0.60-0.64).

CONCLUSIONS

Colonoscopist ADR is associated with MAN. Combining clinical factors and ADR for risk stratification has potential to improve postpolypectomy risk stratification. Improving ADR is likely to improve postpolypectomy outcomes.

Prospective associations of hemoglobin A1c and c-peptide with risk of diabetes-related cancers in the Cancer Prevention Study-II Nutrition Cohort

Self-reported type 2 diabetes mellitus (T2DM) is a risk factor for many cancers, suggesting its pathology relates to carcinogenesis. We conducted a case-cohort study to examine associations of hemoglobin A1c (HbA1c) and c-peptide with cancers associated with self-reported T2DM. This study was drawn from a prospective cohort of 32,383 women and men who provided blood specimens at baseline: c-peptide and HbA1c were assessed in 3,000 randomly selected participants who were cancer-free-at-baseline and an additional 2,281 participants who were cancer-free-at-baseline and subsequently diagnosed with incident colorectal, liver, pancreatic, female breast, endometrial, ovarian, bladder, or kidney cancers. Weighted-Cox regression models estimated hazards ratios (HRs) and 95% confidence intervals (CI), adjusted for covariates. C-peptide was associated with higher risk of liver cancer (per standard deviation (SD) HR: 1.80; 95%CI: 1.32-2.46). HbA1c was associated with higher risk of pancreatic cancer (per SD HR: 1.21 95%CI 1.05-1.40) and with some suggestion of higher risks for all-cancers-of-interest (per SD HR: 1.05; 95%CI: 0.99-1.11) and colorectal (per SD HR: 1.09; 95%CI: 0.98-1.20), ovarian (per SD HR: 1.18; 95%CI 0.96-1.45) and bladder (per SD HR: 1.08; 95%CI 0.96-1.21) cancers. Compared to no self-reported T2DM and HbA1c <6.5% (reference group), self-reported T2DM and HbA1c <6.5% (i.e., T2DM in good glycemic control) was not associated with risk of colorectal cancer, whereas it was associated with higher risks of all-cancers-of-interest combined (HR: 1.28; 95%CI: 1.01-1.62), especially for breast and endometrial cancers. Additional large, prospective studies are needed to further explore the roles of hyperglycemia, hyperinsulinemia, and related metabolic traits with T2DM-associated cancers to better understand the mechanisms underlying the self-reported T2DM-cancer association and to identify persons at higher cancer risk.

Circulating tryptophan metabolites and risk of colon cancer: Results from case-control and prospective cohort studies

Dysregulation of tryptophan metabolism has been linked to colorectal tumorigenesis; however, epidemiological studies investigating tryptophan metabolites in relation to colorectal cancer risk are limited. We studied associations of plasma tryptophan, serotonin and kynurenine with colon cancer risk in two studies with cancer patients and controls, and in one prospective cohort: ColoCare Study (110 patients/153 controls), the Colorectal Cancer Study of Austria (CORSA; 46 patients/390 controls) and the European Prospective Investigation into Cancer and Nutrition (EPIC; 456 matched case-control pairs). Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for colon cancer risk. Tryptophan was inversely associated with colon cancer risk in ColoCare (OR per 1-SD = 0.44; 95% CI, 0.31-0.64) and EPIC (OR per 1-SD = 0.86; 95% CI, 0.74-0.99). Comparing detectable vs nondetectable levels, serotonin was positively associated with colon cancer in CORSA (OR = 6.39; 95% CI, 3.61-11.3) and EPIC (OR = 2.03; 95% CI, 1.20-3.40). Kynurenine was inversely associated with colon cancer in ColoCare (OR per 1-SD = 0.74; 95% CI, 0.55-0.98), positively associated in CORSA (OR per 1-SD = 1.79; 95% CI, 1.27-2.52), while no association was observed in EPIC. The kynurenine-to-tryptophan ratio was positively associated with colon cancer in ColoCare (OR per 1-SD = 1.38; 95% CI, 1.03-1.84) and CORSA (OR per 1-SD = 1.44; 95% CI, 1.06-1.96), but not in EPIC. These results suggest that higher plasma tryptophan may be associated with lower colon cancer risk, while increased serotonin may be associated with a higher risk of colon cancer. The kynurenine-to-tryptophan ratio may also reflect altered tryptophan catabolism during colon cancer development.

Oleic Acid and Insulin as Key Characteristics of T2D Promote Colorectal Cancer Deterioration in Xenograft Mice Revealed by Functional Metabolomics

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers with high mortality worldwide. Type 2 diabetes mellitus (T2D), known as a risk factor of CRC, can promote the deterioration of CRC, but the underlying mechanism is elusive. In this study, we aimed to reveal the relationship between CRC and T2D from the perspective of small-molecule metabolism. First, a list of common dysregulated metabolites in CRC and T2D was obtained by retrieving existing metabolomics publications. Among these metabolites, oleic acid (OA) was found to be able to promote the proliferation and migration of colon carcinoma cell HCT116. Further experiments proved that insulin could significantly strengthen this promotion and showed a synergistic effect with OA. Mechanism study found that OA and insulin acted synergistically through the extracellular signal-regulated kinase (ERK)1/2/c-Myc/cyclin D1 pathway. In addition, the combination of ERK1/2 inhibitor SCH772984 and cyclin-dependent kinase (CDK)4/6 inhibitor palbociclib showed a remarkable inhibitory effect on tumor growth in vivo. Taken together, the current study found that OA plays an important role in CRC development by using a functional metabolomics approach. More importantly, insulin and OA were confirmed to synergistically promote the deterioration of CRC in vitro and in vivo via ERK1/2/c-Myc/cyclin D1 pathway. Our findings may shed light on CRC treatment among the T2D population.

Different factors are associated with conventional adenoma and serrated colorectal neoplasia

Current data shows there are differences in factors associated with colorectal neoplasia based on geographical location and cultural settings. There are no studies focusing on the association between environmental factors and colorectal polyps in Australia. The aim of this study was to prospectively evaluate the association of various factors with different colorectal neoplasia histology. We utilized a simplified one-page questionnaire for patients undergoing colonoscopy for information on age; gender; comorbidities; family history of colorectal cancer; physical activity; smoking; diet; alcohol intake; and body mass index. Factors were then evaluated for association with the presence of: (1) neoplastic lesions; (2) conventional adenomas; (3) neoplastic serrated polyps; (4) any lesions (past and present); and (5) hyperplastic polyps. 291 procedures and 260 patients were included. Factors with a p-value < 0.2 in a univariate regression were included in an initial multivariable regression model. Backwards elimination was then performed, removing one predictor at a time until only significant predictors remained. In the final multivariable model, age≥65, male gender, type-2 diabetes mellitus, active smoking and family history of colorectal cancer were found to be statistically significant predictors for the presence of colorectal neoplasia. However, the significant predictors found for conventional adenomas (older age, male gender and smoking) were different from the significant predictors for neoplastic serrated polyps (type-2 diabetes mellitus and family history of colorectal cancer). Older age, male gender, type-2 diabetes mellitus, and smoking were significantly associated with the presence of colorectal neoplasia. The factors associated with conventional adenomas differed from those associated with neoplastic serrated polyps.

Colorectal Cancer Risk Factors and Screening Among the Uninsured of Tampa Bay: A Free Clinic Study

Introduction

Uninsured patients with low socioeconomic status are at high risk for developing colorectal cancer (CRC), and data on risk factors and prevalence of CRC in this population are limited. The purpose of this study was to assess the risk factors for CRC in uninsured patients from free clinics in the Tampa Bay area of Florida.

Methods

We conducted a retrospective cohort study among patients 50 years or older who were provided service at 9 free clinics in the Tampa Bay area between 2016 and 2018. Demographics, chronic disease characteristics, and screening data were collected via a query of paper and electronic medical records.

Results

Of the 13,982 patients seen, 5,139 (36.8%) were aged 50 years or older. Most were female (56.8%), non-Hispanic White (41.1%), and unemployed (54.9%). Patients with CRC screening were more likely to be employed compared with patients without CRC screening (54.4% vs 44.4%, P = .01). Within the cohort, 725 (22.7%) patients were active smokers, 771 (29.2%) patients currently consumed alcohol, and 23 patients (0.4%) had a history of inflammatory bowel disease. Patients had a median body mass index of 29.4 (interquartile range, 25.4–34.2) kg/m², and 1,455 (28.3%) had diabetes. Documented CRC screening was found among 341 (6.6%) patients.

Conclusion

Uninsured patients had a high prevalence of CRC risk factors but a low reported screening rate for CRC. Free clinics are uniquely positioned to provide patients at high risk for CRC with strategies to decrease their risk and to be screened for CRC.

The Sex Bias of Cancer

In hormone-dependent organs, sex hormones and dysregulated hormone signaling have well-documented roles in cancers of the breast and female reproductive organs including endometrium and ovary, as well as in prostate and testicular cancers in males. Strikingly, epidemiological data highlight significant differences between the sexes in the incidence of various cancers in nonreproductive organs, where the role of sex hormones has been less well studied. In an era when personalized medicine is gaining recognition, understanding the molecular, cellular, and biological differences between men and women is timely for developing more appropriate therapeutic interventions according to gender. We review evidence that sex hormones also shape many of the dysregulated cellular and molecular pathways that lead to cell proliferation and cancer in nonreproductive organs.

Young-onset colorectal cancer is associated with a personal history of type 2 diabetes

BACKGROUND

Colorectal cancer (CRC) is rising in incidence in young adults, and this observation is currently unexplained. We investigated whether having a personal history of type 2 diabetes mellitus (T2D) was a potential risk factor for young-onset colorectal cancer (YOCRC).

METHODS

The South Australian Young Onset (SAYO) CRC study is a series of young adults with CRC below age 55. Ninety unrelated YOCRC cases were recruited to the study. Personal history and detailed family history of T2D were obtained at face-to-face interview and confirmed from medical records. Whole exome sequencing was conducted on germline DNA from each CRC case. Controls for personal history studies of T2D were 240 patients with proven clear colonoscopies and no known CRC predispositions.

RESULTS

The median age of YOCRC cases was 44 years (18-54) and of controls was 45 years (18-54), and 53% of both cases and controls were females (P = 0.99). Left-sided (distal) CRC was seen in 67/89 (75%) of cases. A personal history of T2D was confirmed in 17/90 (19%) YOCRC patients compared with controls (12/240, 5%; P < 0.001; odds ratio = 4.4; 95% confidence interval, 2.0-9.7). YOCRC patients frequently reported at least one first-degree relative with T2D (32/85, 38%). Ten of 87 (12%) of YOCRC cases had CRC-related pathogenic germline variants, however, no pathogenic variants in familial diabetes-associated genes were seen.

CONCLUSIONS

Though the mechanism remains unclear, our observations suggest that there is enrichment for personal history of T2D in YOCRC patients.

IMPACT

A diagnosis of T2D could therefore potentially identify a subset of young adults at increased risk for CRC and in whom early screening might be appropriate.

Comorbidity Risk Score in Association with Cancer Incidence: Results from a Cancer Screenee Cohort

The combined effects of comorbidities can cause cancer incidence, while the effects of individual conditions, alone, might not. This study was conducted to investigate the joint impact of comorbidities on cancer incidence. The dietary score for energy-adjusted intake was calculated by applying a Gaussian graphical model and was then categorized into tertiles representing light, normal, and heavy eating behaviors. The risk point for cancer, according to the statuses of blood pressure, total cholesterol, fasting glucose, and glomerular filtration rate was computed from a Cox proportional hazard model adjusted for demographics and eating behavior. The comorbidity risk score was defined as the sum of the risk points for four comorbidity markers. We finally quantified the hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between the strata of the comorbidity risk score and cancer incidence. A total of 13,644 subjects were recruited from the Cancer Screenee Cohort from 2007–2014. The comorbidity risk score was associated with cancer incidence in a dose-dependent manner (HR = 2.15, 95% CI = 1.39, 3.31 for those scoring 16–30 vs. those scoring 0–8, P-trend < 0.001). Subgroup analysis still showed significant dose-dependent relationships (HR = 2.39, 95% CI = 1.18, 4.84 for males and HR = 1.99, 95% CI = 1.11, 3.59 for females, P-trend < 0.05). In summary, there was a dose-dependent impact of comorbidities on cancer incidence; Highlights: Previous studies have generally reported that hypertension, hypercholesterolemia, diabetes, and chronic kidney disease might predispose patients to cancer. Combining these chronic diseases into a single score, this study found a dose-dependent association between the data-driven comorbidity risk score and cancer incidence.

Prognosis of Patients with Colorectal Cancer with Diabetes According to Medication Adherence: A Population-Based Cohort Study

BACKGROUND

Diabetes mellitus is known to have a negative effect on colorectal cancer survival due to hyperinsulinemia or hyperglycemia, and medications such as metformin, which targets insulin resistance and hyperinsulinemia, have a preventive effect on the risk of death. The aim of this study was to compare the risk of death among patients with colorectal cancer with diabetes with different levels of adherence to oral antidiabetics.

METHODS

National Health Information Database was used, which has all claims data for those who are registered for national health insurance in Korea, from 2002 to 2016, for conducting a retrospective cohort study. Newly diagnosed patients with colorectal cancer among diabetics were followed up from the date of diagnosis until death or December 31, 2016. The medication adherence was calculated as the proportion of days covered (PDC). The HR and 95% confidence interval (CI) for death were estimated using the low-adherence patients as a reference.

RESULTS

A total of 33,841 diabetic patients with newly diagnosed colorectal cancer were followed for an average of 4.7 years. Patients with colorectal cancer with good adherence (PDC ≥ 80%) showed a reduced risk of death [HR (95% CI), 0.82 (0.78-0.86)] compared with those with poor adherence (PDC < 80%). A reduced risk of death was observed for all cancer subsites.

CONCLUSIONS

The maintenance of good medication adherence for diabetes mellitus was related to a favorable prognosis of colorectal cancer.

IMPACT

This study provides evidence that patients with colorectal cancer who are adherent to their diabetes medication will have better survival than patients who are not adherent.

Review: Diabetes, Obesity, and Cancer-Pathophysiology and Clinical Implications

Obesity and diabetes have both been associated with an increased risk of cancer. In the face of increasing obesity and diabetes rates worldwide, this is a worrying trend for cancer rates. Factors such as hyperinsulinemia, chronic inflammation, antihyperglycemic medications, and shared risk factors have all been identified as potential mechanisms underlying the relationship. The most common obesity- and diabetes-related cancers are endometrial, colorectal, and postmenopausal breast cancers. In this review, we summarize the existing evidence that describes the complex relationship between obesity, diabetes, and cancer, focusing on epidemiological and pathophysiological evidence, and also reviewing the role of antihyperglycemic agents, novel research approaches such as Mendelian Randomization, and the methodological limitations of existing research. In addition, we also describe the bidirectional relationship between diabetes and cancer with a review of the evidence summarizing the risk of diabetes following cancer treatment. We conclude this review by providing clinical implications that are relevant for caring for patients with obesity, diabetes, and cancer and provide recommendations for improving both clinical care and research for patients with these conditions.

For colorectal cancer patients with type II diabetes, could metformin improve the survival rate? A meta-analysis

OBJECTIVE

Current research is controversial about whether metformin can improve the survival rate of patients with colon cancer. Therefore, we conducted a meta-analysis to identify the association between metformin and the survival rate of colorectal cancer (CRC) patients with type II diabetes.

METHODS

We conducted a search in databases including Pubmed, EMBASE and Cochrane Library. All articles were published in the last decade, and the quality of each study was evaluated by the Newcastle-Ottawa Scale. Odds ratios (ORs) and its corresponding 95% confidence intervals (CIs) for each study were calculated and summary relative risk estimates with corresponding 95% CIs were generated using the random-effects model. Heterogeneity and publication bias were assessed.

RESULTS

Ten articles were included in this meta-analysis. The included articles were all cohort studies. In a pooled analysis of all studies, metformin using was associated with increased overall survival (OS) rate (OR, 0.54; 95% CI, 0.47 to 0.63) and cancer-specific survival (CS) rate (OR 0.59; 95% CI 0.43 to 0.82) of CRC patients with diabetes. We found that the effect of metformin is associated with geographical region through subgroup meta-analysis.

CONCLUSIONS

Metformin using was associated with an increased OS rate and CS rate of colorectal cancer.

Increased Risk of Site-Specific Cancer in People with Type 2 Diabetes: A National Cohort Study

A retrospective cohort design was used with the objective to evaluate cancer risk among people with type 2 diabetes mellitus (T2DM) in Lithuania. The cohort was established by identifying all patients with the first diagnosis of T2DM in the National Health Insurance Fund database during 2000-2012. Cancer cases were identified by record linkage with the Lithuanian Cancer Registry. Standardized incidence ratios (SIRs) were calculated. Of the 127,290 people that were included, 5959 cases of cancer in men and 6661 cancer cases in women with T2DM were observed. A statistically significant increase in risk for all cancer sites was observed in women, SIR 1.16 (95% CI 1.14-1.19), but not in men, SIR 1.00 (95% CI 0.98-1.03). Among males, a significant increase of liver (SIR 2.11, 95% CI 1.79-2.49]), pancreas (SIR 1.77, 95% CI 1.57-1.99), kidney (SIR 1.46 95% CI 1.31-1.62), thyroid (SIR 1.83, 95% CI 1.32-2.54), colorectal (SIR 1.23, 95% CI 1.14-1.31]), skin melanoma (SIR 1.40, 95% CI 1.11-1.76), and non-melanoma skin (SIR 1.14, 95% CI 1.05-1.23) cancer was observed. For females with T2DM, a significant increase in risk of cancer of the liver (SIR 1.45, 95% CI 1.17-1.79), pancreas (SIR 1.74, 95% CI 1.56-1.93), kidney (SIR = 1.43, 95% CI 1.28-1.60), thyroid (SIR = 1.40, 95% CI 1.22-1.62), breast (SIR = 1.24, 95% CI 1.17-1.31), and corpus uteri (SIR 2.07, 95% CI 1.93-2.21) was observed. In conclusion, people with T2DM in Lithuania had an increased risk of site-specific cancer.

Pre-existing type 2 diabetes is an adverse prognostic factor in patients with renal cell carcinoma

BACKGROUND

Diabetes is a risk factor for various cancers, but its prognostic role in renal cell carcinoma (RCC) is controversial and understudied. This study investigated the prognostic value of type 2 diabetes (T2D) in RCC patients.

METHODS

The clinicopathological and follow-up data of 451 RCC patients undergoing radical or partial nephrectomy at the First Hospital of Shanxi Medical University from 2013 to 2018 were reviewed. Associations of T2D with clinicopathological parameters of RCC were evaluated using the Kaplan-Meier method for survival estimates and Cox regression univariate and multivariate analyses.

RESULTS

Of 451 patients, 74 (16.4%) had T2D. These patients were older, had a higher body mass index, higher incidence rates of hypertension and cardiovascular morbidity, a higher rate of laparoscopic surgery, and smaller neoplasms (all P < .05). Patients with T2D exhibited shorter overall survival (OS; P = .009), cancer-specific survival (CSS; P = .043), and recurrence-free survival (RFS; P = .008) than patients without T2D. Fuhrman grade (hazard ratio [HR] 2.542, 95% confidence interval [CI] 1.115-5.795, P = .026) and T2D (HR 3.391, CI 1.458-7.886, P = .005) were independent predictors of OS; T2D was an independent predictor of CSS (HR = 4.637, 95% CI 1.420-15.139, P = .011) and RFS (HR 3.492, 95% CI 1.516-8.044, P = .003).

CONCLUSIONS

Renal cell carcinoma patients with T2D have a shorter OS and higher recurrence rate and mortality risk than those without T2D.

Recent evidence on modifiable and non-modifiable risk factors for colorectal cancer (CRC): a systematic synopsis of meta-analyses from 2015 to 2017

Colorectal cancer (CRC) is a common cancer with a huge impact on international public health. This review discusses recent evidence on modifiable and non-modifiable risk factors for CRC using a systematic review method. This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines on systematic reviews and meta-analyses of observational studies. The literature search was performed on the Ovid MEDLINE database and included publications from 2015 to 2017, followed by a quality assessment and a narrative synthesis. Of the 90 identified articles, there were 13 meta-analyses with statistically significant results. Seven articles discussed modifiable risk factors and six articles discussed non-modifiable risk. The modifiable risk factors with the highest risk were radiotherapy of prostate cancer (pooled odds ratio 1.68; 95% confidence interval [CI] 1.33–2.12). The non-modifiable risk factors with the highest risk was Lynch syndrome (hazard ratio 135.49; 95% CI 111.55–164.57). This review discovered new and previously known risk factors for CRC. Recent evidence shows that research on CRC risk factors is continuing to grow indicating that more studies on risk factors are needed to optimize CRC prevention and early detection.

A healthy lifestyle pattern has a protective association with colorectal polyps

BACKGROUND

Colorectal cancer is associated with lifestyle characteristics such as diet, physical inactivity, obesity, and smoking, but these are not incorporated in screening recommendations. Moreover, the joint association of these factors with various colorectal polyps is not established.

METHODS

A case-control study, among consecutive subjects aged 40-70 years, undergoing colonoscopy. Cases with colorectal polyps were compared with controls. Detailed information was gathered regarding polyp histology and anatomic location, demographics, medical history, anthropometrics, and lifestyle. The healthy lifestyle index was estimated as the sum of: non-smoking, maintaining a healthy weight, healthy diet, and physical activity.

RESULTS

A total of 788 participants were included (cases n = 403, controls n = 385). The healthy lifestyle index had a negative association with colorectal polyps (OR = 0.72, 95% CI 0.62-0.85, P < 0.001), both adenomas and serrated polyps (OR = 0.75, 0.64-0.89, and OR = 0.59, 0.44-0.79, respectively), and both proximal and distal adenomas (OR = 0.77, 0.62-0.95, and OR = 0.73, 0.59-0.90, respectively). Adherence to ≥ 2 healthy lifestyle components was strongly related with colorectal polyps (OR = 0.50, 0.34-0.75, P = 0.001). Abstinence from smoking, and a healthy diet were the factors most strongly associated with lower odds of colorectal polyps (OR = 0.58, 0.42-0.79, and OR = 0.61, 0.44-0.85, respectively).

CONCLUSIONS

Adherence to a healthy lifestyle (≥2 healthy lifestyle components) is inversely associated with colorectal polyps, especially serrated and distal polyps, with no dose-response association. Components most strongly associated with lower odds of colorectal polyps were maintaining a healthy diet and abstinence from smoking. Lifestyle-related characteristics may assist in risk stratification and are potential goals for colorectal neoplasia prevention.

Association between Cardiovascular Risk and Diabetes with Colorectal Neoplasia: A Site-Specific Analysis

Several studies have shown site-specific differences in colorectal cancer (CRC) with respect to the risk factors. CRC was shown to be associated with cardiovascular risk (CVR) factors, but site-specific variations have not been investigated so far. This study aimed to assess the associations between the prevalence and subsite-specific differences of colorectal neoplasia and established CVR scores or known coronary artery disease (CAD) in a large asymptomatic European screening cohort (N = 2098). Participants underwent simultaneous screening colonoscopy and CVR evaluation, using the Framingham Risk Score and Heart Score. Lesions found in the colonoscopy were classified by location (proximal/distal colon or rectum). More neoplasias were found in the proximal versus the distal colon (p < 0.001). The Framingham Risk Score and Heart Score showed incremental risk for colorectal adenoma, across the tertiles in the proximal and the distal colon (p < 0.001). The prevalence of adenomas in the rectum was much lower, but also here, incremental risk could be shown for the Framingham Risk but not the Heart Risk Score tertiles. Prevalence of adenomas in the proximal colon was higher in subjects with type 2 diabetes (T2DM) (p = 0.006), but no association was found between adenomas and T2DM in the distal colon (p = 0.618) and the rectum (p = 0.071). Males had a higher CVR and more findings, in the screening colonoscopy, as compared to females, however, no site-specific differences were noted. Patients with known CAD and high CVR have an increased risk of colorectal neoplasia in both the proximal and distal colon. Patients with T2DM have a higher risk for neoplasia in the proximal colon.

Risk of colon cancer recurrence in relation to diabetes

PURPOSE

To describe the association between diabetes and colon cancer recurrence.

METHODS

We conducted a cohort study at two integrated health care delivery systems in the United States. Using tumor registry data, we identified patients aged ≥ 18 years when diagnosed with stage I-IIIA adenocarcinomas of the colon during 1995-2014. Pre-existing diabetes was ascertained via diagnosis codes. Medical records were reviewed for eligibility and to abstract recurrence and covariate information. Recurrence was ascertained beginning 90 days after the end of colon cancer treatment (i.e., cohort entry). Recurrence of any cancer or a new primary cancer at any site was a secondary outcome. We used multivariable Cox proportional hazards models to estimate hazard ratios (HR) and 95% confidence intervals (CIs) for the associations between diabetes at cohort entry and study outcomes.

RESULTS

Among the 1,923 eligible patients, 393 (16.7%) had diabetes at cohort entry. Diabetes was not associated with recurrence (HR 0.87; 95% CI 0.56-1.33) or with any subsequent cancer (HR 1.09; 95% CI 0.85-1.40). When the definition of recurrence included second primary colorectal cancer, risk was non-significantly higher in patients with diabetes than without diabetes.

CONCLUSIONS

The risk of colon cancer recurrence appears to be similar in patients with and without diabetes at diagnosis.

IMPACT

Future studies should evaluate the association between diabetes and colorectal cancer outcomes, especially second primary colon cancers, in larger populations.

Epidemiological dimensions of the association between type 2 diabetes and cancer: A review of observational studies

Type 2 diabetes (T2D) is a major cause of complications and death in many countries. The possible causal relation between T2D and cancer has been the aim of many research investigations. In view of the importance of the topic we carried out a narrative review of observational studies to summarize the available evidence of the association between T2D and cancer. To deal with the problem of abundance of published studies, we reviewed up to December 2017, the literature of meta-analyses of observational studies first, then we reviewed cohort studies not reported in meta-analyses because of more recent publication. We found that the association of T2D with risk of colorectal cancer was robust, whereas the evidence of the associations with other cancer sites was lower. Some of the observed associations could be overestimated, due to publication bias, unmeasured confounders (such as obesity) and surveillance bias. In conclusion a probable causal association of T2D with risk of colorectal cancer was confirmed. A possible causal association with pancreatic, endometrial, hepatocellular and gallbladder carcinoma was also found. Substantial uncertainty exists for other cancer sites.

Butyrate suppresses abnormal proliferation in colonic epithelial cells under diabetic state by targeting HMGB1

Butyrate is widely accepted as a proliferation inhibitor in colon cancer but less thoroughly characterized in the colonic epithelium of objects with type 2 diabetes mellitus. The present study investigated the regulatory effect of butyrate on proliferation, the related molecule high-mobility group box 1 (HMGB1) and the receptor for advanced glycation end products (RAGE) in the colon of db/db type 2 diabetic model mice and non-cancerous NCM460 colon cells. Proliferation and the expression of HMGB1 and RAGE were increased and could be partially reversed by butyrate treatment in the colon of db/db mice, which were consistent in NCM460 cells under a high glucose state. In NCM460 cells, under the normal glucose state, proliferation increased by overexpression of HMGB1. Under a high glucose state, increased expression of HMGB1 was accompanied with a release from cell nuclei into the cytoplasm and extracellular matrix. Down-regulation of HMGB1 could lower the expression of RAGE and attenuate the abnormally increased proliferation. And overexpression of HMGB1 reversed the suppressing effect of butyrate on abnormally increased proliferation. Conclusively, butyrate suppressed the abnormally increased proliferation in colonic epithelial cells under diabetic state by targeting HMGB1.

Fasting glucose and risk of colorectal cancer in the Korean Multi-center Cancer Cohort

Previous cohort studies have demonstrated a positive association between diabetes mellitus (DM) and colorectal cancer (CRC). However, there are few comparisons between DM groups categorized by fasting glucose level. This study examined associations between diabetes as defined by fasting glucose level and self-reported history of DM and CRC risk among Korean adults. Data from the Korean Multi-center Cancer Cohort between 1993 and 2005 were analyzed. The study population comprised 14,570 participants aged 20 years or older. Participants were followed until December 31, 2012 (median follow-up: 11.9 years). Among participants with high fasting glucose (≥126mg/dL), the risk of developing CRC was significantly higher (HR: 1.51 [1.02-2.25]) than among participants with low fasting glucose (<126mg/dL). Risk was not significantly higher among participants with self-reported history of DM (HR: 1.34 [0.78-2.31]). When both fasting glucose and history of DM were considered together, the risk of CRC among participants with both high fasting glucose and history of DM was 54% (HR: 1.54 [0.97-2.43]), and the risk of CRC among participants with high fasting glucose and no history of DM was 50% (HR: 1.50 [0.73-3.05]). When the first 5 years of follow-up were excluded, among participants with high fasting glucose, the risk of developing CRC was significantly higher (HR: 1.61 [1.02-2.56]) than among participants with low fasting glucose. Risk of CRC was also significantly higher among participants with high fasting glucose and no history of DM (HR: 1.69 [1.01-2.84]). High fasting glucose and self-reported history of DM were associated with increased risk of CRC in this Korean population.

Diabetes-induced mechanophysiological changes in the small intestine and colon

The disorders of gastrointestinal (GI) tract including intestine and colon are common in the patients with diabetes mellitus (DM). DM induced intestinal and colonic structural and biomechanical remodeling in animals and humans. The remodeling is closely related to motor-sensory abnormalities of the intestine and colon which are associated with the symptoms frequently encountered in patients with DM such as diarrhea and constipation. In this review, firstly we review DM-induced histomorphological and biomechanical remodeling of intestine and colon. Secondly we review motor-sensory dysfunction and how they relate to intestinal and colonic abnormalities. Finally the clinical consequences of DM-induced changes in the intestine and colon including diarrhea, constipation, gut microbiota change and colon cancer are discussed. The final goal is to increase the understanding of DM-induced changes in the gut and the subsequent clinical consequences in order to provide the clinicians with a better understanding of the GI disorders in diabetic patients and facilitates treatments tailored to these patients.

Clinicopathological analysis and risk factors of advanced colorectal neoplasms incidentally detected by 18F-FDG PET-CT

BACKGROUND

As the clinical use of fluorine-18-fluorodeoxyglucose PET-computed tomography (F-FDG PET-CT) has increased, the incidental finding of F-FDG uptake with subsequent diagnosis of advanced neoplasm at colorectum has increased. The aim of this study is to analyze the characteristics and risk factors of advanced colorectal neoplasm incidentally detected by F-FDG PET-CT.

PATIENTS AND METHODS

Patients who underwent colonoscopy because of an incidental finding of F-FDG uptake at the colorectum from January 2006 to January 2015 at Yeungnam University Hospital were reviewed retrospectively. Advanced neoplasm was defined as adenoma of at least 10 mm, adenoma with serrated or villous component, high-grade dysplasia, and adenocarcinoma.

RESULTS

Of the 19 798 candidates, 180 patients with incidental colorectal F-FDG uptake were included in this study. The indications of PET-CT were metastasis work-up, health screening, and others. The male to female ratio was 1.6 : 1 and the mean age was 62.7±11.4 years. A total of 156 lesions were detected in the colorectum and 86 (47.8%) were diagnosed as advanced neoplasms. Of the 86 patients with advanced neoplasms, 34 (39.5%) underwent an operation, 34 (39.5%) underwent endoscopic resection, and 18 (20.9%) underwent chemotherapy or conservative treatments. In univariate analysis, age of 62.5 years or older, carcinoembryonic antigen (CEA) of at least 3.4 ng/ml, maximum standardized uptake value (SUVmax) of at least 8.0, hypertension, F-FDG uptake on the rectosigmoid, and PET-CT for metastasis work-up showed a significant association with advanced neoplasm. In multivariate analysis, CEA (P=0.028), SUVmax (P<0.001) and an indication of PET-CT for metastasis work-up (P=0.008) were independent predictors of advanced neoplasm.

CONCLUSION

Colonoscopy should be recommended in case of F-FDG uptake at the colorectum, particularly in patients with CEA of at least 3.4 ng/ml, SUVmax of at least 8.0, or metastasis work-up of malignancy.

Parameters of Glucose and Lipid Metabolism Affect the Occurrence of Colorectal Adenomas Detected by Surveillance Colonoscopies

PURPOSE

Limited data are available regarding the associations between parameters of glucose and lipid metabolism and the occurrence of metachronous adenomas. We investigated whether these parameters affect the occurrence of adenomas detected on surveillance colonoscopy.

MATERIALS AND METHODS

This longitudinal study was performed on 5289 subjects who underwent follow-up colonoscopy between 2012 and 2013 among 62171 asymptomatic subjects who underwent an initial colonoscopy for a health check-up between 2010 and 2011. The risk of adenoma occurrence was assessed using Cox proportional hazards modeling.

RESULTS

The mean interval between the initial and follow-up colonoscopy was 2.2±0.6 years. The occurrence of adenomas detected by the follow-up colonoscopy increased linearly with the increasing quartiles of fasting glucose, hemoglobin A1c (HbA1c), insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and triglycerides measured at the initial colonoscopy. These associations persisted after adjusting for confounding factors. The adjusted hazard ratios for adenoma occurrence comparing the fourth with the first quartiles of fasting glucose, HbA1c, insulin, HOMA-IR, and triglycerides were 1.50 [95% confidence interval (CI), 1.26-1.77; p(trend)<0.001], 1.22 (95% CI, 1.04-1.43; p(trend)=0.024), 1.22 (95% CI, 1.02-1.46; p(trend)=0.046), 1.36 (95% CI, 1.14-1.63; p(trend)=0.004), and 1.19 (95% CI, 0.99-1.42; p(trend)=0.041), respectively. In addition, increasing quartiles of low-density lipoprotein-cholesterol and apolipoprotein B were associated with an increasing occurrence of adenomas.

CONCLUSION

The levels of parameters of glucose and lipid metabolism were significantly associated with the occurrence of adenomas detected on surveillance colonoscopy. Improving the parameters of glucose and lipid metabolism through lifestyle changes or medications may be helpful in preventing metachronous adenomas.

Diabetes Mellitus and Site-specific Colorectal Cancer Risk in Korea: A Case-control Study

Objectives:

Previous large-scale cohort studies conducted in Korea have found a positive association between diabetes mellitus (DM) and colorectal cancer (CRC) in men only, in contrast to studies of other populations that have found significant associations in both men and women.

Methods:

A total of 1070 CRC cases and 2775 controls were recruited from the National Cancer Center, Korea between August 2010 and June 2013. Self-reported DM history and the duration of DM were compared between cases and controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by binary and polytomous logistic regression models.

Results:

DM was associated with an elevated risk of CRC in both men (OR, 1.47; 95% CI, 1.13 to 1.90) and women (OR, 1.92; 95% CI, 1.24 to 2.98). This association remained when we controlled for age, body mass index, alcohol consumption, and physical activity level. In sub-site analyses, DM was associated with distal colon cancer risk in both men (multivariate OR, 2.04; 95% CI, 1.39 to 3.00) and women (multivariate ORs, 1.99; 95% CI, 1.05 to 3.79), while DM was only associated with rectal cancer risk in women (multivariate OR, 2.05; 95% CI, 1.10 to 3.82). No significant association was found between DM and proximal colon cancer risk in either men (multivariate OR, 1.45; 95% CI, 0.88 to 2.41) or women (multivariate OR, 1.79; 95% CI, 0.78 to 4.08).

Conclusions:

Overall, DM was associated with an increased risk of CRC in Koreans. However, potential over-estimation of the ORs should be considered due to potential biases from the case-control design.

Metformin Improves Overall Survival of Colorectal Cancer Patients with Diabetes: A Meta-Analysis

Introduction. Diabetic population has a higher risk of colorectal cancer (CRC) incidence and mortality than nondiabetics. The role of metformin in CRC prognosis is still controversial. The meta-analysis aims to investigate whether metformin improves the survival of diabetic CRC patients. Methods. PubMed, EMBASE, and Cochrane Library were searched till July 1, 2016. Cohort studies were included. All articles were evaluated by Newcastle-Ottawa Scale. Hazard Ratios (HRs) with 95% confidence intervals (CIs) for each study were calculated and pooled HRs with corresponding 95% CIs were generated using the random-effects model. Heterogeneity and publication bias were assessed. Results. We included seven cohort studies with a medium heterogeneity (I² = 56.1% and p = 0.033) in our meta-analysis. An improved overall survival (OS) for metformin users over nonusers among colorectal cancers with diabetes was noted (HR 0.75; 95% CI 0.65 to 0.87). However, metformin reveals no benefits for cancer-specific survival (HR 0.79, 95%, CI 0.58 to 1.08). Conclusions. Metformin prolongs the OS of diabetic CRC patients, but it does not affect the CRC-specific survival. Metformin may be a good choice in treating CRC patients with diabetes mellitus in clinical settings.

Diabetes mellitus and the risk of glioma: a meta-analysis

Some studies reported a statistically significant inverse association between diabetes mellitus (DM) and risk of gliomas. However, the result is still controversial. We thus did a meta-analysis and summarized the evidence on the incidence of gliomas that has been studied in its association with DM. Seven case-control studies and 4 cohort studies were selected in this meta-analysis (n = 5898251). DM was significantly associated with decreased risk of gliomas (OR = 0.79; 95% CI 0.67 – 0.93; P = 0.004; I² = 59%). In the subgroup analysis of race, Caucasians of DM showed decreased risk of gliomas (OR = 0.81; 95% CI 0.69 – 0.94; P = 0.007). In the subgroup analysis of design, a statistically significant protective effect of DM on gliomas was observed in case-control studies (OR = 0.68; 95 % CI, 0.53–0.87; P = 0.002), while no such effect was observed in cohort studies (OR = 0.97; 95 % CI, 0.83–1.13; P = 0.70). In a further stratified analysis by gender, a significant association was found among males with DM (OR = 0.83; 95 % CI, 0.70–0.99; P = 0.04). No significant association was found between females with DM and gliomas (OR = 0.97; 95 % CI, 0.78–1.21; P = 0.81). In summary, this meta-analysis of current evidence suggests that DM is significantly associated with decreased gliomas risk in Caucasian and males.

Can gallbladder polyps predict colorectal adenoma or even neoplasia? A systematic review

OBJECTIVE

The purpose of the present systematic review is to identify whether an association between gallbladder polyps and colorectal adenoma or neoplasia exists.

DATA SOURCES

We conducted a systematic review searching the Medline (1966-2016), Scopus (2004-2016), ClinicalTrials.gov (2008-2016) and Cochrane Central Register of Controlled Trials CENTRAL (1999-2016) databases together with reference lists from included studies.

STUDY ELIGIBILITY CRITERIA

All prospective and retrospective observational cohort studies were included.

RESULTS

Four studies were finally included which included 17,437 patients. The association between gallbladder polyps and colorectal adenoma or even neoplasia is not unanimously supported. However, a possible association is clearly depicted. According to one study it seems that this correlation seems to become significant only when the gallbladder polyps exceed the size of 5 mm. However, the impact of size of gallbladder polyps was not investigated in the remaining studies.

CONCLUSION

According to the results of our systematic review there is some evidence to support the hypothesis that gallbladder polyps might adequately predict future risk of colorectal neoplasia. At present, however, current knowledge is very limited and the available data scarce. In this context further studies are necessary to be carried out, before the presence of gallbladder polyps on ultrasound can be recommended as an indication to perform a screening colonoscopy on the same patient.

Metformin use and risk of colorectal adenoma after polypectomy in patients with type 2 diabetes mellitus

BACKGROUND

Existing literature suggests that metformin, the most commonly used biguanide, may lower colorectal cancer risk. Because most colorectal cancers originate in precancerous adenomas, we examined whether metformin use lowered colorectal adenoma risk after polypectomy in patients with type-2 diabetes.

METHODS

Retrospective cohort study of 40- to 89-year-old Kaiser Permanente Northern California patients who had type 2 diabetes, and ≥1 adenoma detected at baseline colonoscopy during 2000 to 2009 and a repeat colonoscopy 1 to 10 years from baseline adenoma diagnosis through 2012. Cox models evaluated the association between metformin use during follow-up and subsequent adenoma diagnoses, controlling for age, race/ethnicity, sex, body mass index, and repeat examination indication.

RESULTS

Study included 2,412 patients followed for a median of 4.5 years; cumulatively, 1,117 (46%) patients had ≥1 adenoma at repeat colonoscopy. Compared with patients not receiving diabetes medications (n = 1,578), metformin-only use (n = 457) was associated with lower adenoma recurrence risk [adjusted HR, 0.76; 95% confidence interval (CI), 0.65-0.89], and the association was stronger with increasing total metformin dose [quartile (Q) 1: HR, 0.90; 95% CI, 0.72-1.12; Q2: HR, 0.89; 95% CI, 0.70-1.12; Q3: HR, 0.80; 95% CI, 0.63-1.01; Q4: HR, 0.50; 95% CI, 0.42-0.60, Ptrend < 0.001]. Findings were unchanged in sensitivity analyses, including evaluating only outcomes during the 3- to 10-year period from baseline.

CONCLUSION

Our study suggests a potential benefit of metformin use in lowering the risk of subsequent adenomas after polypectomy in patients with type 2 diabetes.

IMPACT

Metformin may lower colorectal cancer risk by reducing the formation of precancerous lesions, reinforcing the potential additional benefits of its use.