Prevalence of diagnosed cancer according to duration of diagnosed diabetes and current insulin use among U.S. adults with diagnosed diabetes: findings from the 2009 Behavioral Risk Factor Surveillance System

Diabetes and skin cancers: Risk factors, molecular mechanisms and impact on prognosis

Diabetes and skin cancers have emerged as threats to public health worldwide. However, their association has been less intensively studied. In this narrative review, we explore the common risk factors, molecular mechanisms, and prognosis of the association between cutaneous malignancies and diabetes. Hyperglycemia, oxidative stress, low-grade chronic inflammation, genetic, lifestyle, and environmental factors partially explain the crosstalk between skin cancers and this metabolic disorder. In addition, diabetes and its related complications may interfere with the appropriate management of cutaneous malignancies. Antidiabetic medication seems to exert an antineoplastic effect, however, future large, observation studies with a prospective design are needed to clarify its impact on the risk of malignancy in diabetes. Screening for diabetes in skin cancers, as well as close follow-up for the development of cutaneous malignancies in subjects suffering from diabetes, is warranted.

The odds of neoplasia in dogs with and without diabetes mellitus

BACKGROUND

Increased risk of neoplasia in humans with diabetes mellitus (DM) is well documented. It is unknown if dogs with DM have increased risk of neoplasia.

OBJECTIVE

Determine if dogs with DM have an overall increased risk of neoplasia and risk for specific forms of neoplasia compared to dogs without DM.

ANIMALS

Seven hundred dogs with DM and 700 breed, age, and sex-matched dogs without DM, examined during the same years.

METHODS

Retrospective case-control study. Odds ratios (OR), corresponding 95% confidence intervals (CI), and P-values were calculated using conditional logistic regression to determine if dogs with DM had increased odds of developing neoplasia compared to dogs without DM.

RESULTS

The overall odds of developing neoplasia were not significantly different in dogs with and without DM. However, dogs with DM had significantly higher odds of developing an adrenal mass (OR, 4; 95% CI, 1.1-14.2; P = .03) compared to dogs without DM. The odds of developing a splenic mass in dogs with DM (OR, 1.2; 95% CI, 0.99-1.39) were increased compared to dogs without DM, but this difference was not significant (P = .07).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with DM may be at increased risk for adrenal neoplasia. Awareness of this risk can facilitate early diagnosis of this life-threatening comorbidity. Larger studies are needed to confirm these findings.

Do diabetic complications influence cancer-related events in people with type 2 diabetes? A cohort approach

AIM

To investigate whether diabetic micro- and macrovascular complications (mMVC) influence cancer-related events in people with type 2 diabetes.

METHODS

People with type 2 diabetes from the SURDIAGENE cohort were characterized (duration of diabetes, HbA1c, mMVC, history of cancer) and prospectively followed-up for death and cancer-related events (occurrence, dissemination and cancer-related death).

RESULTS

Between 2002 and 2012, 1468 participants (58% men, mean age 64.8 ± 10.7 years, mean duration of diabetes 14.5 ± 9.9 years at baseline) were enrolled. At baseline, 119 (8%) had a personal history of cancer. Incident cancer occurred in 207 (14%) patients during a mean follow-up of 7.3 ± 3.7 years and was associated with older age, smoking status and personal history of cancer. mMVC were not associated with cancer-related events, considering cancer occurrence, node/metastasis dissemination and cancer-specific death. Risk of all-cause mortality was increased in diabetic patients cumulating cancer history and mMVC (HR 1.73, 95%CI 1.25-2.38) compared to those with neither cancer nor mMVC. In our cohort, cancer-related death was not associated with mMVC (HR 1.05, 95%CI 0.67-1.64), but conversely history of cancer was significantly associated with cardiovascular-related death (HR 2.41, 95%CI 1.36-4.26).

CONCLUSION

In our cohort, mMVC were not associated with cancer-related events, while history of cancer was significantly associated with cardiovascular death.

The Distribution of Cardiovascular-Related Comorbidities in Different Adult-Onset Cancers and Related Risk Factors: Analysis of 10 Year Retrospective Data

Introduction: Understanding the epidemiology of cardiovascular disease (CVD) related comorbidity is a key strategy for improving the outcomes of patients with cancer. Therefore, this study aimed to assess the distribution of cardiovascular comorbidities and cardiovascular risk factors (CVRF) among five cancer sites. Methods: This is a single-centered, cross-sectional study performed in Dalian, China. Between 2008 and 2018, all newly diagnosed cancer in the First Affiliated Hospital of Dalian Medical University, China were screened. Clinical data were extracted from a comprehensive electronic health record system. Results: 35861 patients with lung, colorectal, gastric, breast, and thyroid cancer were collected retrospectively. The most prevalent CVDs in descending order were hypertension (21.9%), followed by coronary heart disease (6.5%), atrial fibrillation (2.9%), and heart failure (1%). The prevalence of hypertension significantly varies between lung (21.3%), colorectal (27.3%), gastric (22.5%), breast (16.7%), and thyroid cancer (22.4%) (P < 0.001). CVRF varies with cancer sites. Age, sex, total cholesterol, triglyceride, low-density lipoprotein cholesterol, systolic blood pressure, smoking, alcohol use, and diabetes mellitus (DM) are common risk factors associated with CVD at different cancer sites. The association between DM and presence of CVD was strong in breast (odds ratio [OR] = 4.472, 95% confidence interval [CI]: 3.075-6.504, P < 0.001), lung (OR = 3.943; 95% CI: 3.270-4.754, P < 0.001), colorectal (OR = 3.049; 95% CI: 2.326-3.996, P < 0.001), and gastric (OR = 2.508; 95% CI: 1.927-3.264, P < 0.001) cancer. Conclusion: Cancer patients had a significant burden of CVD and increased CVRF. The prevalence of CVRF and CVD comorbidity differ for cancer types. DM remains significantly associated with CVD at different cancer sites except for thyroid cancer.

Relation between Baseline Coronary Atherosclerotic Status, Cardiovascular Events, and Malignancies in Type 2 Diabetics: A Long-Term Prospective Cohort Study

INTRODUCTION

Coronary artery disease and malignancy occur more frequently in patients with type 2 diabetes. They may share inflammation as a possible common pathogenetic mechanism, but it is unclear whether a clinical correlation exists between them.

METHODS

This prospective cohort study followed 735 asymptomatic diabetics, aged 63.4 ± 5.3 years (mean ± standard deviation) for 12.2 ± 0.6 years after baseline coronary artery calcium scoring and cardiac computed tomography angiography. We examined extent and nature of coronary atherosclerosis and incidence of clinical cardiovascular (CV) events (death or myocardial infarction) and sought a relation to incidence of malignancy and malignancy mortality.

RESULTS

Total mortality was 16.5% (121/735 patients): malignancy was cause of death in 48/121 (39.7%) of these and CV events in 44/121 (36.3%). There was no relation between extent of coronary atherosclerosis and incident malignancy (plaque volume 127 [21, 427] mm3 (median [interquartile range]) for incident malignancy versus 153 [24, 427] mm3 no malignancy, p = 0.71) or death from malignancy (plaque volume 176 [26, 646] versus 144 [22, 411] mm3, p = 0.32). There was also no relation between presence of high-risk plaque and incident malignancy (high-risk plaque in 27.1% with malignancy vs. 21.6% without, p = 0.18) or fatal malignancy (p = 0.16). Incident and fatal malignancy were not related to clinical CV events. Independent predictors of incident and fatal malignancy were age, smoking at baseline, and elevated C-reactive protein.

CONCLUSION

This study found no relation between extent of coronary atherosclerosis or incidence of CV events and malignancy. Malignancy surpassed CV disease as the commonest long-term cause of mortality in middle-aged and older diabetics.

Effect of type 2 diabetes and antihyperglycemic drug therapy on signs of tumor invasion in papillary thyroid cancer

PURPOSE

This retrospective study investigated the association between worrisome pathological features of papillary thyroid cancer indicative of invasion and type 2 diabetes, as well as antihyperglycemic drug therapy for diabetes.

METHODS

The records of 14,167 patients who had undergone primary surgery for thyroid cancer were retrospectively reviewed and screened for concomitant diabetes. The diabetic and nondiabetic groups were age and gender matched, and further stratified by treatment, including five single antihyperglycemic drugs.

RESULTS

The study population comprised 942 patients, including 471 patients each with and without diabetes. The rate of worrisome pathological features was higher in diabetic patients than in nondiabetic patients (49.26% cf. 30.57%, P < 0.001), mainly reflected by extrathyroidal extension (34.82% cf. 5.94%, P < 0.001) and lymph node metastasis (42.68% cf. 33.55%, P < 0.001). The number of lymph node metastases in those treated with acarbose (0.32) was significantly lower compared with groups given any of the other four antihyperglycemic drugs (ranging from 1.51 to 2.15; P = 0.001 to 0.05).

CONCLUSIONS

Papillary thyroid cancer complicated with type 2 diabetes has a higher risk of invasive tumor growth. Compared with other antihyperglycemic drugs, patients with acarbose had the lowest risk of aggressive tumor growth. These results may evoke pathophysiological hypotheses to be explored in preclinical and clinical studies.

Diabetes pay-for-performance program can reduce all-cause mortality in patients with newly diagnosed type 2 diabetes mellitus

This study aimed to examine the effect of a diabetes pay-for-performance (P4P) program on all-cause mortality in patients with newly diagnosed type 2 diabetes mellitus. Using a Taiwanese representative nationwide cohort, we recruited 5478 patients with newly diagnosed type 2 diabetes enrolled in the P4P program within 5 years after a diagnosis of diabetes between January 1, 2002 and December 31, 2010 and individuals not enrolled in the P4P program were recruited as the control group matched 1:1 with the study group. We used multivariate Cox proportional hazard models analysis to investigate the effect of the P4P program and adherence on all-cause mortality. A total of 250 patients died in the P4P group compared to 395 in the control group (mortality rate 104 vs 169 per 10,000 person-years, respectively, P < .0001). The control group also had more comorbidities. Patients enrolled in the P4P program demonstrated significant long-term survival benefits, of which the adjusted hazard ratio (aHR) for all-cause mortality was 0.58 [95% CI (0.48-0.69)]. In the study group, better adherence to the P4P program resulted in a greater reduction in mortality, with aHRs [95% CI] of 0.48 [0.38-0.62] and 0.36 [0.26-0.49] in subjects with a minimum 1-year and 2-year good P4P adherence, respectively. Participating in the P4P program within 5 years after the diagnosis of diabetes resulted in a significant reduction in all-cause mortality, and this effect was particularly pronounced in the patients with better adherence to the P4P program.

Does long-term use of antidiabetic drugs changes cancer risk?

Antidiabetic medications are commonly used around the world, but their safety is still unclear. The aim of this study was to investigate whether long-term use of insulin and oral antidiabetic medications is associated with cancer risk.We conducted a well-designed case-control study using 12 years of data from Taiwan's National Health Insurance Research Database and investigated the association between antidiabetic medication use and cancer risk over 20 years. We identified 42,500 patients diagnosed with cancer and calculated each patient's exposure to antidiabetic drugs during the study period. We matched cancer and noncancer subjects matched 1:6 by age, gender, and index date, and used Cox proportional hazard regression and conditional logistic regression, adjusted for potential confounding factors, that is, medications and comorbid diseases that could influence cancer risk during study period.Pioglitazone (adjusted odds ratio [AOR], 1.20; 95% confidence interval [CI], 1.05-1.38); and insulin and its analogs for injection, intermediate or long acting combined with fast acting (AOR, 1.22; 95% CI, 1.05-1.43) were significantly associated with a higher cancer risk. However, metformin (AOR, 1.00; 95% CI, 0.93-1.07), glibenclamide (AOR, 0.98; 95% CI, 0.92-1.05), acarbose (AOR, 1.06; 95% CI, 0.96-1.16), and others do not show evidence of association with cancer risk. Moreover, the risk for specific cancers among antidiabetic users as compared with nonantidiabetic medication users was significantly increased for pancreas cancer (by 45%), liver cancer (by 32%), and lung cancer (by 18%).Antidiabetic drugs do not seem to be associated with an increased cancer risk incidence except for pioglitazone, insulin and its analogs for injection, intermediate or long acting combined with fast acting.

Insulin receptor plays a central role in skin carcinogenesis by regulating cytoskeleton assembly

Diabetes mellitus prevalence is increasing rapidly and is a major cause of mortality and morbidity worldwide. In addition to the known severe complications associated with the disease, in recent years diabetes has been recognized as a major risk factor for cancer. Patients with diabetes experience significantly higher incidence of and higher mortality rates from many types of cancer. However, to date there are no conclusive data on the pathophysiology underlying the association between these two diseases. We previously reported that insulin regulates skin proliferation and differentiation, while IGF1 had different sometimes contrasting effects to those of insulin, suggesting direct involvement of insulin in transformation. To this end, we developed an epidermal skin-specific insulin receptor knockout (SIRKO) mouse, in which the insulin receptor (IR) is inactivated only in skin, with no other metabolic consequences. We found that IR inactivation by itself resulted in a marked decrease in skin tumorigenesis. In the control group 100% of the mice developed tumors, but in the SIRKO group tumor incidence was over 60% lower, and 25% of the SIRKO mice did not develop tumors at all, and the tumors that did develop were smaller and benign in their appearance. Furthermore, IR inactivation in vitro not only prevented cell transformation but also reversed the keratinocyte-transformed phenotype. We found that IR inactivation led to a striking abnormality in the major keratin cytoskeleton filaments structure in both in vivo and in vitro, a change that we were able to link to the decreased transformation potential in IR-null cells. In summary, we identified a unique pathway in which IR regulates cytoskeletal assembly, thus affecting skin transformation, opening a new potential target for cancer treatment and prevention.-Weingarten, G., Ben Yaakov, A., Dror, E., Russ, J., Magin, T. M., Kahn, C. R., Wertheimer, E. Insulin receptor plays a central role in skin carcinogenesis by regulating cytoskeleton assembly.

Differences in risk factors of malignancy between men and women with type 2 diabetes: A retrospective case-control study

BACKGROUND

The aim of this multicenter, retrospective, case-control study was to identify differences in risk factors of malignancy between men and women with type 2 diabetes.

RESULTS

Among women the most prevalent malignancies were: breast and uterine cancers (35.6% and 14.4% respectively), while among men there were: colorectal and prostate cancers (24.5% and 13.3% respectively). In both gender metformin use was associated with lower cancer risk. Obesity and insulin treatment in dose-dependent and time-varying manner were associated with significantly increased risk of malignancy in females. In men, unexpectedly, cardiovascular disease was more prevalent in control group. Other variables did not show significant association with malignancy risk.

MATERIALS AND METHODS

118 women and 98 men with type 2 diabetes mellitus who developed cancer after diagnosis of diabetes and the same number of strictly age matched controls with type 2 diabetes and without malignancy were included into the study. Diabetes duration, antidiabetic medications use, glycated hemoglobin level, body mass index, smoking habits, occupation, presence of comorbidities and aspirin use were included into analyses.

CONCLUSIONS

Metformin demonstrated protective effect against cancer in both sexes. Obesity and insulin treatment seem to have greater impact on cancer risk among women.

Risk factors for cancer development in type 2 diabetes: A retrospective case-control study

BACKGROUND

The risk of several types of cancer is increased in type 2 diabetes mellitus. The earliest possible diagnosis of cancer - difficult within regular outpatient diabetes care - is of utmost importance for patients' survival. The aim of this multicenter, retrospective (years 1998-2015), case-control study was to identify risk factors associated with malignancy in subjects with diabetes treated in a typical outpatient setting.

METHODS

In the databases of 3 diabetic and 1 primary care clinics 203 patients (115 women) with type 2 diabetes mellitus who developed malignancy while treated for diabetes were identified. The control group consisted of 203 strictly age- and gender matched subjects with type 2 diabetes without cancer. Factors associated with diabetes: disease duration, antidiabetic medications use and metabolic control of diabetes were analyzed. Also other variables: BMI (body mass index), smoking habits, place of residence and comorbidities were included into analysis.

RESULTS

The most prevalent malignancies in men and women together were breast cancer (20.7 %) and colorectal cancer (16.3 %). HbA1c (hemoglobin A1c) level ≥8.5 %, obesity and insulin treatment in dose-dependent and time-varying manner demonstrated significant association with increased risk of malignancy, while metformin use was associated with a lower risk of cancer. Diabetes duration, comorbidities, smoking habits, place of residence and aspirin use did not show significant association with risk of malignancy.

CONCLUSIONS

In the outpatient setting the obese patients with poorly controlled insulin treated type 2 diabetes mellitus should be rigorously assessed towards malignancies, particularly breast cancer in women and colorectal cancer in men.

Metformin association with lower prostate cancer recurrence in type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Accumulating evidence suggests that metformin possesses anticarcinogenic properties, and its use is associated with favorable outcomes in several cancers. However, it remains unclear whether metformin influences prognosis in prostate cancer (PCa) with concurrent type 2 diabetes (T2D).

MATERIALS AND METHODS

We searched PubMed, EMBASE, and the Cochrane Library from database inception to April 16, 2014 without language restrictions to identify studies investigating the effect of metformin treatment on outcomes of PCa with concurrent T2D. We conducted a meta-analysis to quantify the risk of recurrence, progression, cancer-specific mortality, and all-cause mortality. Summary relative risks (RRs) with corresponding 95% confidence intervals (CIs) were calculated. Publication bias was assessed by Begg's rank correlation test.

RESULTS

A total of eight studies fulfilled the eligibility criteria. We found that diabetic PCa patients who did not use metformin were at increased risk of cancer recurrence (RR, 1.20; 95%CI, 1.00-1.44), compared with those who used metformin. A similar trend was observed for other outcomes, but their relationships did not reach statistical significance. Funnel plot asymmetry was not observed among studies reporting recurrence (p=0.086).

CONCLUSIONS

Our results suggest that metformin may improve outcomes in PCa patients with concurrent T2D. Well-designed large studies and collaborative basic research are warranted.

Long-term insulin glargine therapy in type 2 diabetes mellitus: a focus on cardiovascular outcomes

Cardiovascular disease is the leading cause of mortality in type 2 diabetes mellitus. Hyperinsulinemia is associated with increased cardiovascular risk, but the effects of exogenous insulin on cardiovascular disease progression have been less well studied. Insulin has been shown to have both cardioprotective and atherosclerosis-promoting effects in laboratory animal studies. Long-term clinical trials using insulin to attain improved diabetes control in younger type 1 and type 2 diabetes patients have shown improved cardiovascular outcomes. Shorter trials of intensive diabetes control with high insulin use in higher risk patients with type 2 diabetes have shown either no cardiovascular benefit or increased all cause and cardiovascular mortality. Glargine insulin is a basal insulin analog widely used to treat patients with type 1 and type 2 diabetes. This review focuses on the effects of glargine on cardiovascular outcomes. Glargine lowers triglycerides, leads to a modest weight gain, causes less hypoglycemia when compared with intermediate-acting insulin, and has a neutral effect on blood pressure. The Outcome Reduction With Initial Glargine Intervention (ORIGIN trial), a 6.2 year dedicated cardiovascular outcomes trial of glargine demonstrated no increased cardiovascular risk.

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.

Reduced risk of lung cancer with metformin therapy in diabetic patients: a systematic review and meta-analysis

Emerging evidence from epidemiologic studies and basic science suggests an inverse association between metformin use and cancer risk in diabetic patients. However, the association with lung cancer is not consistent. We summarized the evidence currently available (2009-2013) and explored sources of heterogeneity. Metformin therapy was associated with significantly lower risks of cancers of the lung (4 studies; pooled relative risk = 0.71, 95% confidence interval (CI): 0.55, 0.95; P = 0.02) and respiratory system (6 studies; pooled relative risk = 0.85, 95% CI: 0.75, 0.96; P = 0.01). There was evidence of moderate heterogeneity (I(2) > 50%). The major sources of heterogeneity were smoking adjustment status and cancer site. The relative risk from studies that adjusted for smoking was 1.16-fold (95% CI: 1.00, 1.35) closer to the null than that from studies not adjusting for smoking. The relative risk of respiratory cancer was 1.23-fold (95% CI: 1.02, 1.49) closer to the null than that for lung cancer. In conclusion, metformin use appears to be associated with lower risks of lung and respiratory cancer in diabetic patients. However, caution regarding overestimation is needed, since adjustment for smoking attenuates the association.

Diabetes and cancer relationships

Diabetes and cancer are both heterogeneous and multifactorial diseases with tremendous impact on health worldwide. Epidemiologic evidence suggests that certain malignancies may be associated with diabetes, as well as with diabetes risk factors and, perhaps, with certain diabetes treatments. Numerous biological mechanisms could account for these relationships. Insulin-like growth factor (IGF)-1, IGF-2, IGF-1 receptors, insulin, and the insulin receptor play roles in the development and progression of cancers. Although evidence from randomized controlled trials does not support or refute associations of diabetes and its treatments with either increased or reduced risk of cancer incidence or prognosis, consideration of malignancy incidence rates and the magnitude of the trials that would be required to address these issues explains why such studies may not be readily undertaken.

Diabetes mellitus and colorectal cancer prognosis: a meta-analysis

BACKGROUND

Diabetes mellitus is associated with an increased incidence of colorectal cancer, but the impact of diabetes mellitus on colorectal cancer prognosis is not clear.

OBJECTIVE

We conducted a meta-analysis of observational studies to examine the association between preexisting diabetes mellitus and colorectal cancer all-cause mortality, cancer-specific mortality, and recurrence.

DATA SOURCES

Medline and Embase were searched through August 22, 2012.

STUDY SELECTION

We included studies reporting all-cause mortality, cancer-specific mortality, disease-free survival, or recurrence in patients who have colorectal cancer according to diabetic status.

INTERVENTION

Meta-analyses were performed by the use of random-effects models.

MAIN OUTCOME MEASURES

The primary outcomes measured were all-cause mortality, cancer-specific mortality, and disease-free survival.

RESULTS

Twenty-six articles met our inclusion criteria. Patients with colorectal cancer who had diabetes mellitus had a 17% increased risk of all-cause mortality (relative risk, 1.17; 95% CI, 1.09-1.25) and a 12% increased risk of cancer-specific mortality (relative risk, 1.12; 95% CI, 1.01-1.24) in comparison with those who did not have diabetes mellitus. Those with diabetes mellitus also had poorer disease-free survival (relative risk, 1.54; 95% CI, 1.08-2.18) compared with their nondiabetic counterparts. In subgroup analyses, diabetes mellitus was associated with all-cause mortality in both rectal (relative risk, 1.24; 95% CI, 1.07-1.29) and colon cancer patients (relative risk, 1.17; 95% CI, 1.07-1.29). Sensitivity analyses including only patients with nonmetastatic disease identified stronger associations between diabetes mellitus and both all-cause (relative risk, 1.32; 95% CI, 1.21-1.44) and cancer-specific (relative risk, 1.27; 95% CI, 1.06-1.52) mortality.

LIMITATIONS

Some studies had short follow-up or did not report mean or median follow-up. The included studies were heterogeneous in study population, diabetes mellitus diagnostic criteria, and outcome ascertainment.

CONCLUSION

Patients with colorectal cancer who have diabetes mellitus are at greater risk for all-cause and cancer-specific mortality and have worse disease-free survival than those who do not have diabetes mellitus. Studies are warranted to determine whether the proper treatment could attenuate the excess mortality among patients with colorectal cancer who have diabetes mellitus.

Clinical and molecular mechanisms favoring cancer initiation and progression in diabetic patients

Cancer incidence and mortality are higher among diabetic patients. This review examines the mechanisms, both general and site-specific, for this increase. Hyperglycemia and hyperinsulinemia, which are the major abnormalities that characterize diabetes, can promote cancer via both independent and synergic mechanisms. Insulin is both a metabolic hormone and a growth factor that promotes cell proliferation. When insulin levels are increased due to either insulin resistance or insulin treatment, their mitogenic effect is more marked in malignant cells that frequently overexpress the insulin receptor and, more specifically, its A isoform that has predominant mitogenic activity. Hyperglycemia provides energy for malignant cell proliferation and, via the peculiar energy utilization of cancer cells, favors cancer growth and neoangiogenesis. Additionally, diabetes-associated obesity has cancer-promoting effects due to mechanisms that are specific to excess fat cells (such as increased peripheral estrogens, increased pro-mitogen cytokines and growth factors). Also fat-associated chronic inflammation can favor cancer via the cell damage caused by reactive oxygen species (ROS) and via the production of inflammatory cytokines and transcription factors that stimulate cancer growth and invasiveness. Finally, the multiple drugs involved in the treatment of diabetes can also play a role. Diabetes-associated comorbidities, tissue-specific inflammation, and organ-specific dysfunctions can explain why the risk of cancer can differ by tissue type among diabetic patients. The increased risk of cancer-related mortality is moderate among individual patients with diabetes (RR = 1.25), but the pandemic nature of the disease means that a considerable number of lives could be spared through a better understanding of the factors associating diabetes and cancer.