Type 2 diabetes mellitus associated with increased risk for colorectal cancer: evidence from an international ecological study and population-based risk analysis in China

The global burden of colorectal cancer attributable to high plasma glucose in 204 countries and territories, 1990-2019: an analysis of the Global Burden of Disease Study

OBJECTIVES

This study aimed to estimate the burden of colorectal cancer (CRC) attributable to high plasma glucose from 1990 to 2019.

STUDY DESIGN AND METHODS

Data on the disease burden were retrieved from the Global Burden of Disease online database. Estimated average percentage change (EAPC) was used to quantify the age-standardized mortality rate (ASMR) and age-standardized disability-adjusted life years (DALYs) rate (ASDR) of high plasma glucose-related CRC trends by sex and location between 1990 and 2019.

RESULTS

Globally, the death number and DALYs of CRC attributable to high plasma glucose remained a steady increase at global level from 1990 to 2019, and similar trends have been reported in age-standardized rate. The country with the largest number of death cases and DALYs of high plasma glucose-related CRC in 2019 was China, followed by the United States of America and India. Nearly three-quarters of total countries experienced an increase in the ASMR and ASDR, and the greatest increase of ASMR and ASDR was found in Uzbekistan (EAPC = 5.32) and Equatorial Guinea (EAPC = 4.65), respectively. A negative correlation was found between sociodemographic indices and the EAPC of ASMR and ASDR (r_ASMR = -0.259, p < 0.001; r_ASDR = -0.282, p < 0.001).

CONCLUSIONS

A significant increase in mortality and DALYs of CRC attributable to high plasma glucose was observed in global and most countries, especially in the developing countries. Public health policies and targeted programs are needed to reduce the burden of disease.

Current cancer burden in China: epidemiology, etiology, and prevention

Cancer has become the most common cause of death in China. Owing to rapid economic development, improved livelihood, and shifts in risk factors, cancer epidemiology has experienced substantial changes during the past several decades. In this review, we aim to describe the current cancer epidemiology of the main types of cancer in China, report major risk factors associated with cancer development, and summarize the contributions of the Chinese government to controlling the cancer burden. A total of 4,064,000 new cases were diagnosed in China in 2016. The most frequent types are lung cancer (828,100; 20.4%), colorectal cancer (408,000; 10.0%), and gastric cancer (396,500; 9.8%). Lung (657,000; 27.2%), liver (336,400, 13.9%), and stomach (288,500; 12.0%) cancers are the 3 most deadly cancers in the general population. The 5-year survival rate for cancer has dramatically increased in recent decades. However, liver and particularly pancreatic cancers still have the poorest prognosis. The main modifiable risk factors associated with cancer development include infectious agents, smoking, alcohol consumption, obesity, unhealthful dietary habits, and inadequate physical activity. The Chinese government has made unremitting efforts to decrease the cancer burden, including cancer education and investment in cancer screening programs.

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.

Effects of Diabetes on Inflammatory Status and Prognosis in Cancer Patients

Background

Cancer and diabetes mellitus (DM) are prevalent, but there still a lack of convinced evidence clearly explaining the extent of the effect of diabetes in cancer.

Data and Methods

Clinical data of 2,929 cancer patients were collected. Diabetes were diagnosed according to the Diabetes Diagnosis and Treatment Criteria. BMI was classified by the BMI standards for Chinese adults published by the Working Group on Obesity. All involved patients were classified into the non-DM group and DM group. The Kaplan–Meier curve, log-rank test and Cox regression analyses were used to perform survival analysis.

Results

Compared with non-DM patients, OS in DM patients was significant shorter in lung cancer (HR = 2.076, P = 0.001 in early stage; HR = 2.118, P < 0.001 in advanced stage), digestive tract cancer (HR = 1.768, P = 0.020 in early stage; HR = 2.454, P = 0.005 in advanced stage), leukemia (HR = 2.636, P < 0.001), breast cancer (HR = 2.495, P = 0.047 in early stage; HR = 2.929, P = 0.019 in advanced stage) and liver cancer (HR = 3.086, P < 0.001 in early stage; HR = 2.219, P = 0.049 in advanced stage). DM negatively influenced OS when the BMI was within the normal range in overall cancer (HR = 2.468, P < 0.001), lung cancer (HR = 2.297, P < 0.001), digestive tract cancer (HR = 2.354, P < 0.001), liver cancer (HR = 2.406, P = 0.001), leukemia (HR = 4.039, P < 0.001) and breast cancer (HR = 4.222, P = 0.008). Among those with BMI ≥ 24 kg/m², DM played a role only in lung cancer (HR = 1.597, P = 0.037).

Conclusions

Patients with diabetes tend to combine worse body composition and inflammation status, and that glycemic control can ameliorate the impairment of diabetes to some extent.

ASSOCIATION BETWEEN DIABETICS AND INTESTINAL CANCER WITH THE RISK OF MUTATION IN CD38 GENE IN IRANIAN POPULATION

BACKGROUND

Intestinal cancer often occurs in type 2 diabetic patients. The concept of increasing insulin levels and insulin-like growth factor in the blood with type 2 diabetes are stimulated with the growth and depletion of cloned cell walls, and the continuation of this process leads to the cellular deformation. This is the evidence for intestinal cancer in type 2 diabetes in population.

OBJECTIVE

In this study, we aimed to find out the relationship between diabetics and intestinal cancer based on CD38 gene mutation.

METHODS

Samples were collected from 200 population including normal and case ones. PCR products related to rs 6449181 of CD38 gene was amplified with ARMS-PCR technique, and a 420-bp sharp banding was observed as well. According three ARMS-PCR techniques, three primers were designed by oligo7 software. Primers include F1, F2 and R (amplifying for normal, mutant and reverse primer respectively).

RESULTS

This band was observed using a primer F1 that carries the wild type nucleotide using a primer, and when it is used with the F2 primer, it brings the mutant primer to populations of patients with diabetes and diabetes-cancer. In addition, the clinical results including body mass index, blood glucose and insulin level were analyzed. The means ±SD and Tuckey's post hoc test were significant between the clinical characterization parameters between cases and healthy populations. The allelic gene frequencies and Hardy-Weinberg equilibrium between nucleotides were evaluated, and the significant level between the alleles and gene frequencies was observed.

CONCLUSION

In general, the current study found that there is a relationship between diabetes and intestinal cancer among the studied populations.

Epidemiology and risk factors of colorectal cancer in China

In China, colorectal cancer (CRC) ranked fourth and fifth in the highest incidence and mortality rates of all malignancies in 2018, respectively. Although these rates are below the world average, China placed first worldwide in the number of new CRC cases and CRC-related deaths because of its comparatively large population. This disease represents a threat to the health of population and incurs a heavy economic burden on the society and individuals. CRC has various risk factors, including age, sex, lifestyle, genetic factors, obesity, diabetes, gut microbiota status, and precancerous lesions. Furthermore, incidence and mortality rates of CRC are closely related to socioeconomic development levels, varying according to regional and population characteristics. Prevention is the main strategy to reduce incidence and mortality rates of CRC. This can be achieved through strategies stimulating lifestyle changes, healthy diet habits, and early screening for high-risk individuals. To reduce the burden of CRC, public health officials should promote prevention and management of modifiable risk factors through national policies. The rising incidence and mortality rates of CRC in China may be timely curbed by clarifying specific epidemiological characteristics, optimizing early screening strategies, and strictly implementing diagnosis and treatment guidelines. Thus, this study aimed to collect and report the current research status on epidemiology and risk factors of CRC in China.

Cancer risk in Chinese diabetes patients: a retrospective cohort study based on management data

The excess risk of cancer observed in patients with type 2 diabetes (T2DM) may have been influenced by detection bias. The aim of this study was to examine the real association by evaluating time-varying site-specific cancer risks in newly diagnosed T2DM patients. A total of 51,324 registered cancer-free individuals newly diagnosed with T2DM between 2004 and 2014 were linked with the Shanghai Cancer Registry and the Vital Statistics through September 2015. A total of 2920 primary, invasive cancer cases were identified during 325,354 person-years period. Within 1 year following diabetes onset, participants with T2DM had higher risks of total, lung and rectal cancer in men and total, liver, pancreas, thyroid, breast and uteri cancer in women. Thereafter the incidence for overall cancer decreased and then increased along with follow-up time, with the upward trend varying by cancer, suggesting potential detection bias. After the initial 1-year period, standardized incidence ratios (SIR) and 95% CIs for overall cancer were 0.80 (95% CI 0.76-0.85) in men and 0.93 (95% CI 0.88-0.99) in women, but a higher risk of breast and thyroid cancers were observed in women, with SIR and 95% CI being 1.13 (1.01, 1.28) and 1.37 (1.11, 1.63), respectively. Our results suggest that T2DM patients are at higher risk of certain cancers; this risk particularly increases shortly after diabetes diagnosis, which is likely to be due to detection bias caused by increased ascertainment. Prevention of female breast and thyroid cancers should be paid attention in Chinese individuals with T2DM.

Type 2 diabetes and risk of colorectal cancer in two large U.S. prospective cohorts

Background

Previous studies have shown a positive association between type 2 diabetes (T2D) and colorectal cancer (CRC) risk. However, it is uncertain whether this association differs by duration of T2D or sex. We thus investigated the associations of T2D and its duration with the risk of incident CRC.

Methods

We followed 87,523 women from the Nurses’ Health Study (1980–2012) and 47,240 men from the Health Professionals Follow-up Study (1986–2012). Data on physician-diagnosed T2D was collected at baseline with a questionnaire and updated biennially. Cox regression models were used to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

Results

We documented 3000 CRC cases during up to 32 years of follow-up. Among men, T2D was associated with increased risk of CRC compared to those without T2D (HR: 1.42; 95% CI: 1.12–1.81). This positive association persisted in sensitivity analyses by excluding CRC identified within 1 year of diabetes diagnosis and patients with T2D who used hypoglycaemic medications. Among women, T2D was positively, but not statistically significantly, associated with CRC risk (HR: 1.17; 95% CI: 0.98–1.39).

Conclusions

Our findings support that T2D was associated with a moderately higher risk of developing CRC in men; a weaker, nonsignificant positive association was observed in women.

Sex differences in the association between diabetes and cancer: a systematic review and meta-analysis of 121 cohorts including 20 million individuals and one million events

AIMS/HYPOTHESIS

Diabetes has been shown to be a risk factor for some cancers. Whether diabetes confers the same excess risk of cancer, overall and by site, in women and men is unknown.

METHODS

A systematic search was performed in PubMed for cohort studies published up to December 2016. Selected studies reported sex-specific relative risk (RR) estimates for the association between diabetes and cancer adjusted at least for age in both sexes. Random-effects meta-analyses with inverse-variance weighting were used to obtain pooled sex-specific RRs and women-to-men ratios of RRs (RRRs) for all-site and site-specific cancers.

RESULTS

Data on all-site cancer events (incident or fatal only) were available from 121 cohorts (19,239,302 individuals; 1,082,592 events). The pooled adjusted RR for all-site cancer associated with diabetes was 1.27 (95% CI 1.21, 1.32) in women and 1.19 (1.13, 1.25) in men. Women with diabetes had ~6% greater risk compared with men with diabetes (the pooled RRR was 1.06, 95% CI 1.03, 1.09). Corresponding pooled RRRs were 1.10 (1.07, 1.13) for all-site cancer incidence and 1.03 (0.99, 1.06) for all-site cancer mortality. Diabetes also conferred a significantly greater RR in women than men for oral, stomach and kidney cancer, and for leukaemia, but a lower RR for liver cancer.

CONCLUSIONS/INTERPRETATION

Diabetes is a risk factor for all-site cancer for both women and men, but the excess risk of cancer associated with diabetes is slightly greater for women than men. The direction and magnitude of sex differences varies by location of the cancer.

Diabetes mellitus and the risk of gastrointestinal cancer in women compared with men: a meta-analysis of cohort studies

Background

The increasing epidemic proportions of diabetes mellitus (DM) are a major cause of premature illness and death. However, whether DM confers the same excess risk of gastrointestinal cancer for women as it does for men remains controversial. The purpose of this study was to estimate the relation between DM and gastrointestinal cancer in women compared with men after accounting for other major risk factors based on cohort studies.

Methods

We performed a meta-analysis of cohort studies published through May 2017 from PubMed, Embase, and the Cochrane Library. Studies with cohort designs were stratified by sex and reported the relation between DM and esophageal cancer (EC), gastric cancer (GC), colorectal cancer (CRC), colon cancer (CC), rectal cancer (RC), hepatocellular carcinoma (HCC), or pancreatic cancer (PC) risk. The ratio of relative risk (RRR) between men and women was employed to measure the sex differences in the relation between DM and gastrointestinal cancer with a random effects model with inverse variance weighting.

Results

We included 38 cohort studies reporting data on 18,060,698 individuals. The pooled RRR indicated DM women was associated with an increased risk of GC (RRR: 1.14; 95%CI: 1.06–1.22; p < 0.001), while the risk of HCC was lower (RRR: 0.88; 95%CI: 0.79–0.99; p = 0.031) as compared with DM men. Further, there was no evidence of sex differences in the RRR between participants who had DM compared with those without DM for EC (p = 0.068), CRC (p = 0.618), and PC (p = 0.976). In addition, the pooled RRR showed a statistically significant association between DM and the risk of CC in women compared with men (RRR: 0.93; 95%CI: 0.86–1.00; p = 0.050), and there was no evidence of sex differences for RC among participants with DM compared to those without DM (p = 0.648). Finally, the sex differences of the comparison between DM and non-DM for gastrointestinal cancer risk at different sites were variable after stratification for different effect estimates.

Conclusions

The findings of this study suggested female-to-male RRR of DM was increased for GC, while reduced for HCC and CC. However, there were no sex differences for the relation between DM and the risk of EC, CRC, PC, and RC.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4351-4) contains supplementary material, which is available to authorized users.

Obesity, Diabetes and Gastrointestinal Malignancy: The role of Metformin and other Anti-diabetic Therapy

The association between Diabetes and cancer has been known for decades with obesity and insulin resistance being postulated as the main underlying risk factors for both disorders. With rise of the epidemic of obesity in the USA and around the globe, there has been a rise in diabetes that is currently reaching epidemic proportions. Diabetes is known to be associated with increased risk of several types of malignancy including breast, cervical, pancreatic and colon cancer. In this review, we discuss the epidemic of obesity and its consequential epidemic of diabetes highlighting the pathophysiologic mechanisms of increased cancer in the diabetic population. We will then discuss the role of insulin therapy as well as, other antidiabetic medications, particularly metformin that has been to be associated with lower risk as well as better survival with GI malignancies based on several studies including a study that was recently published by our group.

Incidence and Mortality Risks of Cancer in Patients with Type 2 Diabetes: A Retrospective Study in Shanghai, China

Background: Evidence from epidemiologic investigation indicates that people with type 2 diabetes (T2DM) are at a significantly higher risk of many types of cancer and mortality. The aim of this study was to investigate the incidence and mortality risks of cancer in patients with T2DM compared with the general population in Shanghai, China. Methods: Based on the Shanghai Diabetes Registry (SDR) database linking to the Shanghai Cancer Registry and Surveillance System (SCRSS), a total of 12,276 T2DM patients without cancer were defined and followed up from 1 December 2001 to 31 July 2011. Standardized incidence ratio (SIR) and standardized mortality ratio (SMR) with 95% confidence interval (CI) were calculated using the whole gender and age-matched general population of Shanghai as a reference during the same period. Results: The overall cancer risk was found higher in both males and females T2DM patients, with the SIR of 3.14 (95% CI 2.73–3.56) and 4.29 (95% CI 3.64–4.94), respectively. The overall mortality risk of cancer also significantly increased with the SMR of 2.27 (95% CI 1.86–2.68) and 1.86 (95% CI 1.46–2.26), respectively. Pancreatic cancer was with the highest SIR and SMR in both genders. Conclusions: Compared with the general population, patients with T2DM were associated with higher incidence and mortality risks of cancer, especially pancreatic cancer.

Predictors of all-cause and cardiovascular-specific mortality in type 2 diabetes: A competing risk modeling of an Iranian population

BACKGROUND

In Asian population, diabetes mellitus is increasing and has become an important health problem in recent decades. In Iran, cardiovascular disease (CVD) accounts for nearly 46% of the total costs spent for diabetes-associated diseases. Because individuals with diabetes have highly increased CVD risk compared with normal individuals, it is important to diagnosis factors that may increase CVD risk in diabetic patients. The study objective was to identify predictors associated with CVD mortality in patients with type 2 diabetes (T2D) and to develop a prediction model for cardiovascular (CV)-death using a competing risk approach.

MATERIALS AND METHODS

The study population consisted of 2638 T2D (male = 1110, female = 1528) patients aged ≥35 years attending from Endocrine and Metabolism Research Center in Isfahan for a mean follow-up period of 12 years; predictors for different cause of death were evaluated using cause specific Cox proportional and subdistribution hazards models.

RESULTS

Based on competing modeling, the increase in blood pressure (BP) (spontaneously hypertensive rats [SHR]: 1.64), cholesterol (SHR: 1.55), and duration of diabetes (SHR: 2.03) were associated with CVD-death. Also, the increase in BP (SHR: 1.85), fasting blood sugar (SHR: 2.94), and duration of diabetes (SHR: 1.68) were associated with other death (consist of cerebrovascular accidents, cancer, infection, and diabetic nephropathy).

CONCLUSIONS

This finding suggests that more attention should be paid to the management of CV risk in type 2 diabetic patients with high cholesterol, high BP, and long diabetes duration.

A Linear Dose-Response Relationship between Fasting Plasma Glucose and Colorectal Cancer Risk: Systematic Review and Meta-analysis

For many years, the question of whether hyperglycaemia, a manifestation of prediabetes, diabetes mellitus and metabolic syndrome, is a risk factor for colorectal cancer has been intensely studied. In fact, even after the conclusion of several prospective studies, the topic is still controversial. We conducted a systematic review and meta-analysis to investigate the dose-response relationship between blood glucose concentration and the incidence of colorectal cancer. A linear (P = 0.303 for non-linearity) dose-response relationship was observed between fasting plasma glucose (FPG) and colorectal cancer risk without significant heterogeneity. The relative risk (RR) for colorectal cancer per 20 mg/dL increase in FPG was 1.015 (95% CI: 1.012-1.019, P = 0.000). In subgroup analyses, the pooled RRs for colon cancer (CC) and rectal cancer (RC) studies were 1.035 (95% CI 1.008-1.062, P = 0.011) and 1.031 (95% CI: 0.189-5.628, P = 0.972), respectively; in the analysis comparing men and women, the pooled RRs were 1.016 (95% CI: 1.012-1.020, P = 0.000) and 1.011 (95% CI: 0.995-1.027, P = 0.164), respectively. Sensitivity analyses using two methods showed similar results. In conclusion, there is a significant linear dose-response relationship between FPG and the incidence risk of colorectal cancer. For people with diabetes or prediabetes, controlling blood glucose might be useful to prevent colorectal cancer.

Cancer incidence in patients with type 2 diabetes mellitus: a population-based cohort study in Shanghai

BACKGROUND

Type 2 diabetes mellitus (T2DM) has been suggested to increase the risk of cancers. The aim of this study was to investigate the risk of common cancers in Chinese patients with T2DM.

METHODS

A population-based retrospective cohort study including 36,379 T2DM patients was conducted in Minhang District of Shanghai, China, during 2004 to 2010. All T2DM patients were enrolled from the standardized management system based on local electronic information system. Newly-diagnosed cancer cases were identified by record-linkage with the Shanghai Cancer Registry. Standardized incidence ratios (SIR) and 95% confidence interval (CI) were used to estimate the risk of cancers among T2DM patients.

RESULTS

Overall crude incidence rate (CIR) of cancers was 955.21 per 105 person-years in men and 829.57 per 105 person-years in women. Increased risk of cancer was found in both gender, with an SIR being 1.28 (95% CI = 1.17-1.38) in men and 1.44 (95% CI =1.32-1.55) in women. Increased risk of colon (SIR = 1.97; 95% CI = 1.49 to 2.46), rectum (1.72; 1.23 to 2.21), prostate (2.87; 2.19 to 3.56), and bladder cancers (1.98, 1.28 to 2.68) were observed in men and elevated risk of colon (1.67; 1.25 to 2.08), breast (1.66; 1.38 to 1.95), and corpus uteri cancers (2.87; 2.03 to 3.71) were observed in women.

CONCLUSIONS

Our results indicate that Chinese patients with T2DM may have an increased risk of some cancers, and the increase may vary by sub-sites of cancers.

Nursing of colostomy complications

Intestinal colostomy complications are common in patients after colostomy, seriously affecting postoperative quality of life. They not only cause difficulties to postoperative nursing and influence postoperative rehabilitation, but also increase the psychological and economic burden. Reducing the incidence of stoma complications and improving the quality of nursing care are of important significance for improving nursing satisfaction and quality of life. This review aims to elucidate the factors influencing complications after colostomy as well as the types, nursing measures and nursing mode for these complications.

Serum IGFBP7 levels associate with insulin resistance and the risk of metabolic syndrome in a Chinese population

Metabolic syndrome (MetS), one of the major public health concerns, is regarded as the “common soil” of incidence of common chronic diseases and may increase the risk of type 2 diabetes. The predominant underlying mechanism of MetS is insulin resistance (IR). Additionally, previous studies have indicated that IGFBP7 has high affinity of binding with insulin and might induce IR. The objective of this study was to firstly evaluate the associations of serum IGFBP7 levels with IR and MetS with a relatively large sample and population based design. In a population based MetS case-control study, HOMA-IR was used to evaluate the insulin sensitivity and serum IGFBP7 levels were determined with chemiluminescence–linked immunoassay. As a result, the subjects of MetS and IR had higher serum levels of IGFBP7 than control healthy subjects. High serum IGFBP7 levels increased the risk of MetS and IR. Serum IGFBP7 levels were also found to be significantly correlated with metabolic-associated parameters of Waist-to-hip ratio (WHR), HDL and LDL. These findings suggest that serum IGFBP7 levels are associated with IR and MetS, providing new insight into the mechanism of IR and Mets. IGFBP7 may be a potential interventional target for IR and Mets.

Can aspirin reduce the risk of colorectal cancer in people with diabetes? A population-based cohort study

AIM

To evaluate whether aspirin can reduce the risk of colorectal cancer in people with diabetes.

METHODS

We studied ≥ 30-year-old people with diabetes, included in the Longitudinal Health Insurance Database 2005 in Taiwan, who were treated with hypoglycaemic drugs. We used a time-varying Cox regression model to adjust for immortal time bias and to estimate the adjusted hazard ratio and 95% CI for the association between aspirin use and colorectal cancer occurrence.

RESULTS

We studied a total of 60 828 people with diabetes (31 176 men and 29 652 women). Their mean (sd) age was 58.72 (13.33) years. A total of 26 494 people were taking aspirin. Aspirin use 3-5 times/week (moderate frequency) for > 5 years (long duration) was found to reduce the risk of colorectal cancer by 46% (hazard ratio 0.54, 95% CI 0.34-0.86). Aspirin use > 5 times/week (high frequency) for 4-5 years (moderate duration) and > 5 years reduced the risk of colorectal cancer by 56 and 68%, respectively (hazard ratio 0.44, 95% CI 0.24-0.80; hazard ratio 0.32, 95% CI 0.20-0.50). Low frequency (≤ 2 times/week) and/or short duration (≤ 3 years) of aspirin use did not reduce the risk of colorectal cancer.

CONCLUSIONS

Aspirin use with high frequency and long duration reduced the risk of colorectal cancer in people with diabetes in a frequency- and duration-dependent manner, whereas low frequency and/or short duration of aspirin use did not. The dosage, frequency and duration of aspirin use that are sufficient to prevent the incidence of colorectal cancer in people with diabetes require further study.

CARING (CAncer Risk and INsulin analoGues): the association of diabetes mellitus and cancer risk with focus on possible determinants - a systematic review and a meta-analysis

Background:

Patients suffering from diabetes mellitus (DM) may experience an increased risk of cancer; however, it is not certain whether this effect is due to diabetes per se.

Objective:

To examine the association between DM and cancers by a systematic review and meta-analysis according to the PRISMA guidelines.

Data Sources:

The systematic literature search includes Medline at PubMed, Embase, Cinahl, Bibliotek.dk, Cochrane library, Web of Science and SveMed+ with the search terms: “Diabetes mellitus”, “Neoplasms”, and “Risk of cancer”.

Study Eligibility Criteria:

The included studies compared the risk of cancer in diabetic patients versus non-diabetic patients. All types of observational study designs were included.

Results:

Diabetes patients were at a substantially increased risk of liver (RR=2.1), and pancreas (RR=2.2) cancer. Modestly elevated significant risks were also found for ovary (RR=1.2), breast (RR=1.1), cervix (RR=1.3), endometrial (RR=1.4), several digestive tract (RR=1.1-1.5), kidney (RR=1.4), and bladder cancer (RR=1.1). The findings were similar for men and women, and unrelated to study design. Meta-regression analyses showed limited effect modification of body mass index, and possible effect modification of age, gender, with some influence of study characteristics (population source, cancer- and diabetes ascertainment).

Limitations:

Publication bias seemed to be present. Only published data were used in the analyses.

Conclusions:

The systematic review and meta-analysis confirm the previous results of increased cancer risk in diabetes and extend this to additional cancer sites. Physicians in contact with patients with diabetes should be aware that diabetes patients are at an increased risk of cancer.

Diabetes and cancer: Associations, mechanisms, and implications for medical practice

Both diabetes mellitus and cancer are prevalent diseases worldwide. It is evident that there is a substantial increase in cancer incidence in diabetic patients. Epidemiologic studies have indicated that diabetic patients are at significantly higher risk of common cancers including pancreatic, liver, breast, colorectal, urinary tract, gastric and female reproductive cancers. Mortality due to cancer is moderately increased among patients with diabetes compared with those without. There is increasing evidence that some cancers are associated with diabetes, but the underlying mechanisms of this potential association have not been fully elucidated. Insulin is a potent growth factor that promotes cell proliferation and carcinogenesis directly and/or through insulin-like growth factor 1 (IGF-1). Hyperinsulinemia leads to an increase in the bioactivity of IGF-1 by inhibiting IGF binding protein-1. Hyperglycemia serves as a subordinate plausible explanation of carcinogenesis. High glucose may exert direct and indirect effects upon cancer cells to promote proliferation. Also chronic inflammation is considered as a hallmark of carcinogenesis. The multiple drugs involved in the treatment of diabetes seem to modify the risk of cancer. Screening to detect cancer at an early stage and appropriate treatment of diabetic patients with cancer are important to improve their prognosis. This paper summarizes the associations between diabetes and common cancers, interprets possible mechanisms involved, and addresses implications for medical practice.

Cancer risks among patients with type 2 diabetes: a 10-year follow-up study of a nationwide population-based cohort in Taiwan

BACKGROUND

This study aims to determine cancer risks among patients with type 2 diabetes through a follow-up study on a nationwide population-based cohort that included Taiwanese diabetic patients and general population in Taiwan as well as to estimate the population attributable fraction (PAF) of site-specific cancer risks that can be attributed to type 2 diabetes in Taiwanese population by using standardized incidence ratios (SIRs, 95% CI).

METHODS

Subjects with type 2 diabetes consisted of 472,979 patients aged ≥ 20 years, whereas general population consisted of 9,411,249 individuals of the same age limit but are not diabetic. Subjects were identified from 1997 to 1998 and followed up until December 31, 2007 or until the first manifestation of any cancer.

RESULTS

Cancer sites with increased risks in men, which were consistent with the main and sensitivity analyses, included pancreas (SIR=1.62; 95% CI=1.53 to 1.72), liver (1.61; 1.57 to 1.64), kidney (1.32; 1.25 to 1.40), oral (1.16, 1.12 to 1.21), and colorectal (1.19, 1.15 to 1.22). Cancer sites with increased risks in women included liver (1.55; 1.51 to 1.60), pancreas (1.44; 1.34 to 1.55), kidney (1.38; 1.30 to 1.46), endometrium (1.36; 1.26 to 1.47), bladder (1.19; 1.11 to 1.27), colorectal (1.16; 1.13 to 1.20), and breast (1.14; 1.09 to 1.18). Overall, PAFs were highest for liver cancer in men (4.0%) and women (3.7%), followed by pancreas (3.4%) and kidney (1.6%) cancers in men, and then for endometrium (1.8%) and kidney (1.8%) cancers in women.

CONCLUSION

Our data suggested that increased cancer risks are associated with type 2 diabetes.

Canola oil influence on azoxymethane-induced colon carcinogenesis, hypertriglyceridemia and hyperglycemia in Kunming mice

Azoxymethane (AOM) is a potent genotoxic carcinogen which specifically induces colon cancer. Hyperlipidemia and diabetes have several influences on colon cancer development, with genetic and environmental exposure aspects. Here, we investigated plasma lipid and glucose concentrations in Kunming mice randomized into four groups; control (no AOM or oil exposure), AOM control, AOM + pork oil, and AOM + canola oil. Aberrant crypt foci (ACF), plasma cholesterol, plasma triglyceride, plasma glucose and organ weight were examined 32 weeks after AOM injection. Results revealed that AOM exposure significantly increased ACF number, plasma triglyceride and glucose level. Further, male mice displayed a much higher plasma triglyceride level than female mice in the AOM control group. Dietary fat significantly inhibited AOM-induced hypertriglyceridemia, and canola oil had stronger inhibitory effect than pork oil. AOM-induced hyperglycemia had no sex-difference and was not significantly modified by dietary fat. However, AOM itself not change plasma cholesterol level. AOM significantly increased liver and spleen weight in male mice, but decreased kidney weight in female mice. On the other hand, mice testis weight decreased when fed canola oil. AOM could induce colorectal carcinogenesis, hypertriglyceridemia and hyperglycemia in Kunming mice at the same time, with subsequent studies required to investigate their genome association.

Detection rate of colorectal neoplasms by opportunistic colonoscopy

AIM: To investigate the detection rate of colorectal neoplasms by opportunistic colonoscopy.

METHODS: In total, 32694 patients who visited Department of Gastroenterology of our hospital from January 2012 to September 2013 were randomly divided into a case group and a control group. The case group was tested by opportunistic colonoscopy, while the control group was tested based on the clinical pattern. The difference in the detection rate of colorectal neoplasms was compared between the two groups.

RESULTS: Of 16298 patients in the trial group, 1167 underwent colonoscopy and the detection rate of colorectal neoplasms was 1.38% (225/16298). Of 16396 patients in the control group, 855 underwent colonoscopy and the detection rate of colonoscopy was 1.07% (176/16396). The detection rate of colorectal neoplasms differed significantly between the two groups (x² = 6.209, P = 0.014).

CONCLUSION: The detection rate of colorectal neoplasms by opportunistic colonoscopy is higher than that based on the clinical pattern.

All-cause, cardiovascular, and cancer mortality rates in postmenopausal white, black, Hispanic, and Asian women with and without diabetes in the United States: the Women's Health Initiative, 1993-2009

Using data from the Women's Health Initiative (1993-2009; n = 158,833 participants, of whom 84.1% were white, 9.2% were black, 4.1% were Hispanic, and 2.6% were Asian), we compared all-cause, cardiovascular, and cancer mortality rates in white, black, Hispanic, and Asian postmenopausal women with and without diabetes. Cox proportional hazard models were used for the comparison from which hazard ratios and 95% confidence intervals were computed. Within each racial/ethnic subgroup, women with diabetes had an approximately 2-3 times higher risk of all-cause, cardiovascular, and cancer mortality than did those without diabetes. However, the hazard ratios for mortality outcomes were not significantly different between racial/ethnic subgroups. Population attributable risk percentages (PARPs) take into account both the prevalence of diabetes and hazard ratios. For all-cause mortality, whites had the lowest PARP (11.1, 95% confidence interval (CI): 10.1, 12.1), followed by Asians (12.9, 95% CI: 4.7, 20.9), blacks (19.4, 95% CI: 15.0, 23.7), and Hispanics (23.2, 95% CI: 14.8, 31.2). To our knowledge, the present study is the first to show that hazard ratios for mortality outcomes were not significantly different between racial/ethnic subgroups when stratified by diabetes status. Because of the "amplifying" effect of diabetes prevalence, efforts to reduce racial/ethnic disparities in the rate of death from diabetes should focus on prevention of diabetes.

Higher rate of colorectal cancer among patients with pyogenic liver abscess with Klebsiella pneumoniae than those without: an 11-year follow-up study

AIM

Pyogenic liver abscess (PLA) has been reported as an early manifestation of colorectal cancer (CRC) in adults, but few studies have investigated this relationship. It is unclear if patients with Klebsiella pneumoniae PLA are at increased risk of subsequent CRC. Our aims were to estimate the incidence of CRC among patients with PLA and to compare the incidence of CRC between K. pneumoniae PLA and non-K. pneumoniae PLA groups.

METHOD

We conducted a retrospective study of patients with PLA diagnosed between 2000 and 2009 at a medical centre in northern Taiwan. CRC status and survival status were determined until December 2010. Incidence data from the general population were retrieved from the Taiwan Cancer Registry. Outcome measures were defined as standardized incidence ratio and the incidence rate per 100,000 person-years.

RESULTS

This study included 2294 patients, of whom 1194 (52%) had K. pneumoniae infection. During the follow-up period, 54 (2.3%) patients were diagnosed with CRC, corresponding to an overall incidence rate of 669.1 (95% CI, 490.7-847.6) per 100,000 person-years. The adjusted hazard ratio of CRC was 2.68 times greater for patients with K. pneumoniae PLA than for those with non-K. pneumoniae PLA (95% CI, 1.40-5.11).

CONCLUSION

Patients with K. pneumoniae PLA had a significantly higher rate of subsequent CRC than did patients with non-K. pneumoniae PLA. Colonoscopy is recommended to detect occult colonic malignancy in patients with PLA, particularly for patients over 60 years of age and with K. pneumoniae.

Racial disparities in colorectal cancer incidence by type 2 diabetes mellitus status

PURPOSE

Type 2 diabetes mellitus (T2DM) prevalence has increased dramatically in the United States since the early 1970s. Though T2DM is known to be associated with colorectal cancer (CRC), information on racial differences in the relationship between T2DM and CRC is limited.

METHODS

Using a retrospective cohort design, we compared the association between T2DM and CRC, including subsites of the colon, in African Americans (AAs) and European Americans (EAs) in South Carolina, a region with large racial disparities in rates of both diseases. A total of 91,836 individuals who were ≥30 years old on 1 January 1990 and had ≥12 months of South Carolina Medicaid eligibility between 1 January 1990 and 31 December 1995 were included in the analyses. Cancer data from 1996 to 2007 included information on anatomic subsite.

RESULTS

Subjects who had T2DM (n = 6,006) were >50 % more likely to be diagnosed with colon cancer compared to those without T2DM (n = 85,681). The association between T2DM and colon cancer was higher in AAs [odds ratio (OR) = 1.72 (95 % confidence interval: 1.21, 2.46); n = 47,984] than among EAs (OR = 1.24; 0.73, 2.11; n = 43,703). Overall, individuals with T2DM were over twice as likely to be diagnosed with in situ or local colon cancer (OR = 2.12; 1.40, 3.22; n = 191) compared to those without T2DM, with a higher likelihood among AAs (OR = 2.49; 1.52, 4.09; n = 113).

CONCLUSIONS

Results from a Medicaid population in a high-risk region of the United States showed an increased likelihood of CRC with T2DM and suggest a racial disparity that disfavors AAs and provides further impetus for efforts aimed at diabetes prevention in this group.

Diabetes mellitus and the incidence and mortality of colorectal cancer: a meta-analysis of 24 cohort studies

AIM

The incidence and mortality of colorectal cancer (CRC) were quantified in persons with and without diabetes mellitus (DM).

METHOD

Medline and Embase were searched for articles published before July 2010. Cohort studies that evaluated incidence and mortality of DM and CRC were included. The initial search identified 1887 titles, of which 24 articles met the inclusion criteria. We defined the relative risk (RR) as the metric of choice; 95% confidence intervals (CIs) were calculated with a random-effects model.

RESULTS

There was an increase in the RR of developing CRC in persons with DM compared with those without DM (RR 1.28; 95% CI 1.19-1.39), without heterogeneity between studies (P(heterogeneity) = 0.13). The association between duration of DM and CRC incidence was stronger in the 11-15-year group (RR 1.51; 95% CI 1.12-2.03) than in the <10-year group (RR 1.05; 95% CI 0.90-1.22) and the >15-year group (RR 1.25; 95% CI 0.80-1.94), and there was significant heterogeneity among subgroups (P(heterogeneity) = 0.01). In studies reporting standardized incidence ratios (SIRs), there was an increased incidence of CRC with DM (RR 1.27; 95% CI 1.14-1.42; P(heterogeneity) = 0.09), and the association was stronger among men (RR 1.47; 95% CI 1.15-1.86) than women (RR 1.08; 95% CI 1.00-1.17); there was significant heterogeneity among gender (P(heterogeneity) = 0.01).

CONCLUSION

This meta-analysis suggests that individuals with DM have a significant increase in risk of developing CRC.

Increased risk of cancer in patients with type 2 diabetes mellitus: a retrospective cohort study in China

Background

Previous studies indicated that type 2 diabetes mellitus (T2DM) might be associated with the risk of cancer. The aim of this study was to investigate the association between T2DM and the risk of developing common cancers in a Chinese population.

Methods

A population-based retrospective cohort study was carried out in the Nan-Hu district of Jiaxing city, Zhejiang province, China. The incidence of cancer cases among type 2 diabetic patients were identified through record-linkage of the Diabetic Surveillance and Registry Database with the Cancer Database from January 2002 to June 2008. The standardized incidence ratio (SIR) and 95% confidence interval (CI) were estimated for the risk of cancer among the patients with type 2 diabetes.

Results

The overall incidence of cancer was 1083.6 per 10⁵ subjects in male T2DM patients and 870.2 per 10⁵ in females. Increased risk of developing cancer was found in both male and female T2DM patients with an SIR of 1.331 (95% CI = 1.143-1.518) and 1.737 (1.478-1.997), respectively. As for cancer subtypes, both male and female T2DM patients had a significantly increased risk of pancreatic cancer with the SIRs of 2.973 (1.73-4.21) and 2.687 (1.445-3.928), respectively. Elevated risk of liver and kidney cancers was only found in male T2DM patients with SIRs of 1.538 (1.005-2.072) and 4.091 (1.418-6.764), respectively. Increased risks of developing breast cancer [2.209 (1.487-2.93)] and leukemia SIR: [4.167 (1.584- 6.749) ] were found in female patients.

Conclusions

These findings indicated that patients with T2DM have an increased risk of developing cancer. Additional cancer screening should be employed in the management of patients with T2DM.

Diabetes mellitus is an independent risk factor for colorectal cancer

BACKGROUND

Epidemiological studies have suggested positive associations between diabetes and colorectal cancer. However, the findings were inconsistent, especially regarding specific sex or cancer subsite.

AIMS

To conduct a systematic review with meta-analysis to examine the association of diabetes mellitus with risk of colorectal cancer and to investigate whether the association is dependent on sex, cancer subsite, race/ethnicity, or duration of diabetes.

METHODS

Relevant studies were identified by searching Pubmed to May 12, 2011. The reference lists of identified articles were also reviewed. Two authors independently selected the studies and extracted relevant data. The study quality was assessed.

RESULTS

Thirty-nine studies (28 cohort studies and 11 case-control studies) were included in the final analysis. Compared with non-diabetic subjects, the pooled risk estimate of colorectal cancer for diabetic subjects was 1.29 (95% CI = 1.23-1.35). The subgroup analyses revealed that the risk was significantly increased for both genders, for every cancer subsite, and for both short duration and long duration of diabetes. Exposure to diabetes increased the risk of colorectal cancer for White and Asian, whereas there was no evidence of such an association either among Black or native Hawaiians.

CONCLUSIONS

Our results confirmed that subjects with diabetes are at modestly increased risk of developing colorectal cancer.

Diabetes and cancer I: risk, survival, and implications for screening

Type 2 diabetes mellitus (DM) and cancer are common diseases that are frequently diagnosed in the same individual. An association between the two conditions has long been postulated. Here, we review the epidemiological evidence for increased risk of cancer, decreased cancer survival, and decreased rates of cancer screening in diabetic patients. The risk for several cancers, including cancers of the pancreas, liver, colorectum, breast, urinary tract, and endometrium, is increased in patients with DM. In a pooled risk analysis weighting published meta-analytic relative risk (RR) for individual cancer by differences in their incidence rates, we found a population RR of 0.97 (95 % CI, 0.75-1.25) in men and 1.29 (95 % CI, 1.16-1.44) in women. All meta-analyses showed an increased relative risk for cancer in diabetic men, except studies of prostate cancer, in which a protective effect was observed. The relationship between diabetes and cancer appears to be complex, and at present, a clear temporal relationship between the two conditions cannot be defined. DM also impacts negatively on cancer-related survival outcomes and cancer screening rates. The overwhelming evidence for lower cancer screening rates, increased incidence of certain cancers, and poorer prognosis after cancer diagnosis in diabetic patients dictates a need for improved cancer care in diabetic individuals through improved screening measures, development of risk assessment tools, and consideration of cancer prevention strategies in diabetic patients. Part two of this review focuses on the biological and pharmacological mechanisms that may account for the association between DM and cancer.

Association Between Glycosylated Hemoglobin and Intentional Weight Loss in Overweight and Obese Patients With Type 2 Diabetes Mellitus

Purpose

The purpose of this study is to assess the relationship between magnitude of weight loss and improvement in percentage A1C (A1C%) among overweight and obese patients with type 2 diabetes mellitus (DM) undergoing weight reduction.

Methods

Case records of patients enrolled in 2 university-based weight management programs were reviewed. Patients were sampled if they had a diagnosis of DM and had at least 1 documented A1C% reduction from their baseline value. Weight loss treatment was individualized and consisted of a calorie-restricted diet, a behavior modification plan, and a plan for increasing physical activity. Patient weights were measured at bimonthly visits. A1C% was measured every 3 months.

Results

Seventy-two patients formed the study cohort. Mean baseline body mass index was 35.1 kg/m2, mean age was 52.6 years, and 59% were males. Mean starting A1C% was 8.6. Patients achieved significant mean weight loss (10.7 kg) at study exit. Weight loss of 6.5 kg (4.5% of baseline body weight), 12.2 kg (8.7%), and 15.9 kg (10.3%) was required to reduce A1C% by 0.5, 1, and 1.5, respectively, and it took a mean of 5.6, 8.7, and 10.1 months, respectively, to achieve this. After adjustment for antidiabetic medication intake, for every 10% weight loss, the predicted reduction in A1C% was 0.81.

Conclusions

Intentional weight loss of 10% can potentially decrease A1C% by 0.81 among patients with type 2 DM. This finding may be clinically useful in encouraging and counseling a patient attempting weight loss.

Association of total energy intake and macronutrient consumption with colorectal cancer risk: results from a large population-based case-control study in Newfoundland and Labrador and Ontario, Canada

Background

Diet is regarded as one of the most important environmental factors associated with colorectal cancer (CRC) risk. A recent report comprehensively concluded that total energy intake does not have a simple relationship with CRC risk, and that the data were inconsistent for carbohydrate, cholesterol and protein. The objective of this study was to identify the associations of CRC risk with dietary intakes of total energy, protein, fat, carbohydrate, fiber, and alcohol using data from a large case-control study conducted in Newfoundland and Labrador (NL) and Ontario (ON), Canada.

Methods

Incident colorectal cancer cases (n = 1760) were identified from population-based cancer registries in the provinces of ON (1997-2000) and NL (1999-2003). Controls (n = 2481) were a random sample of residents in each province, aged 20-74 years. Family history questionnaire (FHQ), personal history questionnaire (PHQ), and food frequency questionnaire (FFQ) were used to collect study data. Logistic regression was used to evaluate the association of intakes of total energy, macronutrients and alcohol with CRC risk.

Results

Total energy intake was associated with higher risk of CRC (OR: 1.56; 95% CI: 1.21-2.01, p-trend = 0.02, 5^th versus 1^st quintile), whereas inverse associations emerged for intakes of protein (OR: 0.85, 95%CI: 0.69-1.00, p-trend = 0.06, 5^th versus 1^st quintile), carbohydrate (OR: 0.81, 95%CI: 0.63-1.00, p-trend = 0.05, 5^th versus 1^st quintile) and total dietary fiber (OR: 0.84, 95% CI:0.67-0.99, p-trend = 0.04, 5^th versus 1^st quintile). Total fat, alcohol, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, and cholesterol were not associated with CRC risk.

Conclusion

This study provides further evidence that high energy intake may increase risk of incident CRC, whereas diets high in protein, fiber, and carbohydrate may reduce the risk of the disease.

Incidence of malignancies in patients with diabetes mellitus and correlation with treatment modalities in a large Israeli health maintenance organization: a historical cohort study

It has been hypothesized that incidence of and mortality from several malignancies are increased among diabetic patients. Whether certain treatment modalities, including use of metformin, sulfonylureas, or insulins, affect cancer incidence or mortality and whether use of long-acting insulin analogues glargine and detemir may increase cancer incidence more than traditional human insulins are debated. The objective was to investigate the association between specific glucose-lowering agents and cancer incidence in diabetic members of an Israeli health maintenance organization. We studied a cohort of 36,342 diabetic patients aged at least 18 years with no history of cancer or treatment with insulin as of January 1, 2003. For the period from January 2003 to December 2007, we searched pharmacy records for purchases of glucose-lowering agents, including metformin, sulfonylureas, human insulin, and analogue insulins. Incident cancer diagnoses were identified from the health maintenance organization cancer registry. We studied the association of cancer incidence with the use of specific glucose-lowering agents, controlling for age, sex, and baseline glycohemoglobin measurement. Cancer was diagnosed in 6% of the study cohort during 164,652 person-years of follow-up time. Cancer incidence increased with age and varied with medication purchasing patterns. On multivariate analysis, age (hazard ratio [HR], 1.049; confidence interval [CI], 1.045-1.052), male sex (HR, 1.16; CI, 1.065-1.264), and number of insulin purchases (HR, 1.007; CI, 1.001-1.012) were significantly associated with increased cancer risk, whereas number of metformin purchases was associated with reduced cancer risk (HR, 0.996; CI, 0.994-0.998). Male sex, age, and human insulin purchases were associated with increased cancer incidence, whereas metformin purchases were associated with decreased cancer risk. There was a trend for increased cancer incidence associated with use of long-acting insulin analogues, but the number of long-acting insulin analogue users was too small for risk estimates to be conclusive.

Diabetes mellitus and incidence and mortality of colorectal cancer: a systematic review and meta-analysis of cohort studies

Increasing evidence suggests that a history of diabetes mellitus (DM) may be associated with an increased risk of colorectal cancer (CRC). To provide a quantitative assessment of the association between DM and risk of CRC, We evaluated the relation between DM and incidence and mortality of CRC in a systematic review of cohort studies. Full publications of cohort studies were identified in MEDLINE, EMBASE and Science Citation Index Expanded, through February 28, 2011. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were summarized using a random-effects model. Between-study heterogeneity was assessed using the Cochran's Q and I2 statistics. A total of 41 cohort studies (35 articles) were included in this systematic review. Combining 30 cohort studies which presented results on diabetes and CRC incidence, diabetes was associated with an increased incidence of CRC (SRRs 1.27, 95% CI: 1.21-1.34), with evident heterogeneity among studies (P=0.002, I2=48.4%). Subgroup analysis and meta-regression analysis by controlling the confounders showed that the increased incidence of CRC was independent of geographic locations, sex, family history of colorectal cancer, smoking, physical activity and body mass index. Diabetes was also positively associated with CRC mortality (SRR 1.20, 95% CI: 1.03-1.40), with evidence of heterogeneity between studies (P<0.001, I2=81.4%). Results from this systematic review support that compared to non-diabetic individuals, diabetic individuals have an increased risk of CRC.

Is diabetes a causal agent for colorectal cancer? Pathophysiological and molecular mechanisms

The possible relationship between diabetes mellitus (DM) and colorectal cancer (CRC), concerning pathophysiological and molecular mechanisms is highlighted in this review. The most recent and complete articles and developments in this particular field were thoroughly reviewed. Common risk factors, such as obesity, sedentary lifestyle, and Western diet between DM and CRC, led to the theory that DM might be a causal agent for CRC development. Various studies have connected type 2 DM and CRC, either proximal or distal, in both sexes. Additionally, chronic insulin treatment has been linked with increased colorectal tumor risk among type 2 diabetic patients. Interestingly, elevated hemoglobin A1c has been proven to be an independent predictor of aggressive clinical behavior in CRC patients. These mechanisms include the insulin-like growth factor-hyperinsulinemia theory and the participation of oncogenic intracellular signaling pathways. Furthermore, it has been proposed that Cox-2 inhibitors might have a role in decreasing the incidence of CRC. Finally, the use of statins to reduce the risk for colon cancer in patients with diabetes has remained controversial. Diabetic patients over 50 should receive counseling regarding their elevated risk for CRC, and screening colonoscopy should be recommended before initiating insulin therapy. However, there are no current guidelines, and this strategy is not yet applicable to some countries, as the corresponding risk would not allow screening colonoscopy to be adopted. There is strong evidence to indicate that DM is a causal agent for CRC development. This conclusion provides new impetus for re-evaluating CRC screening worldwide.

Prospective study reveals associations between colorectal cancer and type 2 diabetes mellitus or insulin use in men

BACKGROUND & AIMS

Type 2 diabetes mellitus (DM) is associated with an increased risk of colorectal cancer (CRC); it is not clear if this association varies by sex or other factors. Insulin use might also be associated with CRC risk. We investigated associations of type 2 DM and insulin use with CRC risk.

METHODS

The Cancer Prevention Study II Nutrition Cohort is a prospective study of cancer incidence. In 1992 or 1993, adult participants (n = 184,194) completed a detailed, self-administered questionnaire. Follow-up questionnaires were sent in 1997 and every 2 years thereafter. Cox proportional hazards regression analysis was used to calculate relative risks (RR) and 95% confidence intervals (CI), adjusting for covariates.

RESULTS

After exclusions, 73,312 men and 81,663 women remained in the final analytic cohort; 1567 men (227 with type 2 DM) and 1242 women (108 with type 2 DM) were diagnosed with colon or rectal cancer by 2007. Among men, type 2 DM was associated with increased risk of incident CRC compared to not having type 2 DM (RR: 1.24; 95% CI: 1.08-1.44); risk was higher for participants with type 2 DM using insulin (RR: 1.36; 95% CI: 1.05-1.78), and participants with type 2 DM not using insulin (RR: 1.22, 95% CI: 1.04-1.45). Among women, type 2 DM and insulin use were not associated with risk of incident CRC (RR: 1.01; 95% CI: 0.82-1.23 and RR: 0.95; 95% CI: 0.64-1.41, respectively).

CONCLUSIONS

There is a modest association between type 2 DM and CRC among men, but not women. Insulin use is not associated with a substantially increased risk of CRC.