Addressing different biases in analysing drug use on cancer risk in diabetes in non-clinical trial settings--what, why and how?

Handling time-varying treatments in observational studies: A scoping review and recommendations

OBJECTIVE

Time-varying treatments are common in observational studies. However, when assessing treatment effects, the methodological framework has not been systematically established for handling time-varying treatments. This study aimed to examine the current methods for dealing with time-varying treatments in observational studies and developed practical recommendations.

METHODS

We searched PubMed from 2000 to 2021 for methodological articles about time-varying treatments, and qualitatively summarized the current methods for handling time-varying treatments. Subsequently, we developed practical recommendations through interactive internal group discussions and consensus by a panel of external experts.

RESULTS

Of the 36 eligible reports (22 methodological reviews, 10 original studies, 2 tutorials and 2 commentaries), most examined statistical methods for time-varying treatments, and only a few discussed the overarching methodological process. Generally, there were three methodological components to handle time-varying treatments. These included the specification of treatment which may be categorized as three scenarios (i.e., time-independent treatment, static treatment regime, or dynamic treatment regime); definition of treatment status which could involve three approaches (i.e., intention-to-treat, per-protocol, or as-treated approach); and selection of analytic methods. Based on the review results, a methodological workflow and a set of practical recommendations were proposed through two consensus meetings.

CONCLUSIONS

There is no consensus process for assessing treatment effects in observational studies with time-varying treatments. Previous efforts were dedicated to developing statistical methods. Our study proposed a stepwise workflow with practical recommendations to assist the practice.

Avoiding Time-Related Biases: A Feasibility Study on Antidiabetic Drugs and Pancreatic Cancer Applying the Parametric g-Formula to a Large German Healthcare Database

Purpose

Investigating intended or unintended effects of sustained drug use is of high clinical relevance but remains methodologically challenging. This feasibility study aims to evaluate the usefulness of the parametric g-formula within a target trial for application to an extensive healthcare database in order to address various sources of time-related biases and time-dependent confounding.

Patients and Methods

Based on the German Pharmacoepidemiological Research Database (GePaRD), we estimated the pancreatic cancer incidence comparing two hypothetical treatment strategies for type 2 diabetes mellitus (T2DM), i.e., (A) sustained metformin monotherapy vs (B) combination therapy with DPP-4 inhibitors after one year metformin monotherapy. We included 77,330 persons with T2DM who started metformin therapy at baseline between 2005 and 2011. Key aspects for avoiding time-related biases and time-dependent confounding were the emulation of a target trial over a 7-year follow-up period and application of the parametric g-formula.

Results

Over the 7-year follow-up period, 652 out of the 77,330 study subjects had a diagnosis of pancreatic cancer. Assuming no unobserved confounding, we found evidence that the metformin/DPP-4i combination therapy increased the risk of pancreatic cancer compared to a sustained metformin monotherapy (risk ratio: 1.47; 95% bootstrap CI: 1.07–1.94). The risk ratio decreased in sensitivity analyses addressing protopathic bias.

Conclusion

While protopathic bias could not fully be ruled out, and computational challenges necessitated compromises in the analysis, the g-formula and target trial emulation proved useful: Self-inflicted biases were avoided, observed time-varying confounding was adjusted for, and the estimated risks have a clear causal interpretation.

Association Between Statins and Cancer Incidence in Diabetes: a Cohort Study of Japanese Patients with Type 2 Diabetes

BACKGROUND

The antitumor effect of statins has been highlighted, but clinical study results remain inconclusive. While patients with diabetes are at high risk of cancer, it is uncertain whether statins are effective for cancer chemoprevention in this population.

OBJECTIVE

This study evaluated the association between statins and cancer incidence/mortality in patients with type 2 diabetes.

DESIGN

This study was a follow-up observational study of the Japanese Primary Prevention of Atherosclerosis with Aspirin for Diabetes (JPAD) trial, which was a randomized controlled trial of low-dose aspirin in Japanese patients with type 2 diabetes.

PARTICIPANTS

This study enrolled 2536 patients with type 2 diabetes, age 30-85 years, and no history of atherosclerotic cardiovascular disease, from December 2002 until May 2005. All participants recruited in the JPAD trial were followed until the day of any fatal event or July 2015. We defined participants taking any statin at enrollment as the statin group (n = 650) and the remainder as the no-statin group (n = 1886).

MAIN MEASURES

The primary end point was the first occurrence of any cancer (cancer incidence). The secondary end point was death from any cancer (cancer mortality).

KEY RESULTS

During follow-up (median, 10.7 years), 318 participants developed a new cancer and 123 died as a result. Cancer incidence and mortality were 10.5 and 3.7 per 1000 person-years in the statin group, and 16.8 and 6.3 per 1000 person-years in the no-statin group, respectively. Statin use was associated with significantly reduced cancer incidence and mortality after adjustment for confounding factors (cancer incidence: adjusted hazard ratio [HR], 0.67; 95% CI, 0.49-0.90, P = 0.007; cancer mortality: adjusted HR, 0.60; 95% CI, 0.36-0.98, P = 0.04).

CONCLUSIONS

Statin use was associated with a reduced incidence and mortality of cancer in Japanese patients with type 2 diabetes.

Metformin and Biliary Tract Cancer in Patients With Type 2 Diabetes

Aim

This retrospective cohort study evaluated whether metformin use in patients with type 2 diabetes mellitus might reduce the risk of biliary tract cancer (BTC); and explored whether metformin use might affect the overall survival in patients who developed BTC.

Methods

New-onset type 2 diabetes patients aged 25–75 years during 1999–2005 were enrolled from the Taiwan’s National Health Insurance and followed up until December 31, 2011. A total of 287,995 ever users and 16,229 never users were identified (unmatched original cohort) and a 1:1 matched pairs of 16,229 ever users and 16,229 never users based on propensity score (PS) were created (matched cohort). Hazard ratios were estimated by three Cox regression models: 1) adjusted for PS; 2) incorporated with the inverse probability of treatment weighting using PS; and 3) all covariates treated as independent variables. Overall survival was compared between ever users and never users of metformin who developed BTC.

Results

In the unmatched cohort, 73 never users and 523 ever users developed BTC, with respective incidence of 100.36 and 38.06 per 100,000 person-years. An overall risk reduction was observed in metformin users in all three regression models with respective hazard ratio (95% confidence interval) of 0.442 (0.344-0.568), 0.377 (0.295-0.481), and 0.477 (0.370-0.615). The tertile analyses showed a dose-response pattern with a neutral effect in the first tertile when metformin use was <2 years and a significant risk reduction in the second and third tertiles. Findings in the matched cohort were consistent with those observed in the unmatched cohort. The overall survival did not differ significantly between ever and never users of metformin among patients who developed BTC.

Conclusions

Metformin significantly reduces the overall risk of BTC by 50%–60%. A dose-response effect is observed and users of approximately 2 years show significantly reduced risk. However, metformin does not affect the overall survival in patients with BTC.

In vitro cytogenetic assessment and comparison of vildagliptin and sitagliptin

Vildagliptin and sitagliptin are commonly used antidiabetic drugs. Chromosomal aberration (CA), sister chromatid exchange (SCE) and cytokinesis-block micronucleus (CBMN) assays were employed to assess and compare cytotoxic and genotoxic effects of these drugs. Peripheral lymphocytes were exposed to 125 μg/ml, 250 μg/ml and 500 μg/ml of vildagliptin and 250 μg/ml, 500 μg/ml and 1000 μg/ml of sitagliptin for 24 h and 48 h with and without exogenous metabolic activation. At the end of the study, it was determined that these drugs and their metabolites had no genotoxic effects on CA, SCE and CBMN. On the other hand, parallel to the increase in dose, vildagliptin showed weak cytotoxicity on the mitotic index, and depending on its increase in dose; sitagliptin caused potential cytotoxicity and cytostatic effect on the mitotic index, nuclear division index and proliferation index. Due to their cytotoxic and cytostatic potential, these drugs inhibit cell proliferation.

Metformin and Reduced Risk of Cancer in the Hong Kong Diabetes Registry: Real Effect or Immortal Time Bias?

BACKGROUND

Whether metformin reduces cancer risk has been hotly debated. One common opinion is that the observed beneficial effects of metformin are the consequence of immortal time bias.

OBJECTIVE

To examine whether the observed beneficial effects of metformin on cancer risk are the consequence of immortal time bias.

DESIGN

Retrospective cohort study.

PARTICIPANTS

A cohort of 3485 patients who started metformin before or at enrollment, 1226 patients who initiated metformin after enrollment, and an unexposed group of 1392 patients who never used metformin.

MAIN MEASURES

Metformin users were categorized into 11 groups in terms of length of time between metformin initiation and enrollment. The percent changes in immortal person-time were calculated for each group.

RESULTS

As the groups of current metformin users (n = 3485) were added sequentially to the metformin group with potential immortal time bias (n = 1226), the proportion of immortal person-time decreased gradually by 74%. As the immortal time decreased, the association between metformin and cancer risk remained statistically significant (uncorrected hazard ratio 0.54, 95% confidence interval 0.42-0.69, P < 0.0001).

CONCLUSION

The change in the association between metformin and cancer is small compared with the changes in the proportion of immortal time, suggesting that immortal time bias does not account for the observed beneficial effect of metformin on cancer risk. Further studies are warranted to confirm this finding in other cohort studies.

Bias in pharmacoepidemiologic studies using secondary health care databases: a scoping review

BACKGROUND

The availability of clinical and therapeutic data drawn from medical records and administrative databases has entailed new opportunities for clinical and epidemiologic research. However, these databases present inherent limitations which may render them prone to new biases. We aimed to conduct a structured review of biases specific to observational clinical studies based on secondary databases, and to propose strategies for the mitigation of those biases.

METHODS

Scoping review of the scientific literature published during the period 2000-2018 through an automated search of MEDLINE, EMBASE and Web of Science, supplemented with manually cross-checking of reference lists. We included opinion essays, methodological reviews, analyses or simulation studies, as well as letters to the editor or retractions, the principal objective of which was to highlight the existence of some type of bias in pharmacoepidemiologic studies using secondary databases.

RESULTS

A total of 117 articles were included. An increasing trend in the number of publications concerning the potential limitations of secondary databases was observed over time and across medical research disciplines. Confounding was the most reported category of bias (63.2% of articles), followed by selection and measurement biases (47.0% and 46.2% respectively). Confounding by indication (32.5%), unmeasured/residual confounding (28.2%), outcome misclassification (28.2%) and "immortal time" bias (25.6%) were the subcategories most frequently mentioned.

CONCLUSIONS

Suboptimal use of secondary databases in pharmacoepidemiologic studies has introduced biases in the studies, which may have led to erroneous conclusions. Methods to mitigate biases are available and must be considered in the design, analysis and interpretation phases of studies using these data sources.

Prevalence and identification of type 1 diabetes in Chinese adults with newly diagnosed diabetes

AIM

This study aimed to estimate the prevalence of latent autoimmune diabetes of adults (LADA) and classic type 1 diabetes mellitus (T1DM) in newly diagnosed adult diabetes in China.

METHOD

This cross-sectional study involved 17,349 newly diagnosed diabetes in adults aged ≥30 years from 46 hospitals within 31 months. Demographic characteristics, clinical features, and medical history were collected by trained researchers. T1DM as a whole was comprised of classic T1DM and LADA. Classic T1DM was identified based on the clinical phenotype of insulin-dependency, and LADA was differentiated from patients with initially an undefined diabetes type with standardized glutamic acid decarboxylase autoantibody testing at the core laboratory. The age and sex distributions from a large national survey of diabetes in China conducted in 2010 were used to standardize the prevalence of classic T1DM and LADA.

RESULTS

Among 17,349 adult patients, the prevalence of T1DM was 5.49% (95% CI: 4.90-6.08%) (5.14% [95% CI: 4.36-5.92%] in males and 6.16% [95% CI: 5.30-7.02%] in females), with 65% of these having LADA. The prevalence of classic T1DM decreased with increasing age (p<0.05), while that of LADA was stable (p>0.05). The prevalence of T1DM in overweight or obese patients was 3.42% (95% CI: 3.20-3.64%) and 2.42% (95% CI: 1.83-3.01%), respectively, and LADA accounted for 76.5% and 79.2% in these two groups.

CONCLUSION

We draw the conclusion that T1DM, especially LADA, was prevalent in newly diagnosed adult-onset diabetes in China, which highlights the importance of routine islet autoantibodies testing in clinical practice.

Regional Differences in the Prevalence of Coronary Heart Disease and Stroke in Patients With Type 2 Diabetes in China

BACKGROUND

There are large regional variations in the prevalence and mortality of cardiovascular disease in general populations in China. It remains uncertain whether the prevalence in type 2 diabetes mellitus (T2DM) varies by region in China.

METHODS

We analyzed data of 219,522 Chinese patients with T2DM retrieved from the China National HbA1c Surveillance System in 2012. We used the Chinese population distribution in 2010 to standardize prevalence of coronary heart disease (CHD), stroke, and composite of both in 30 provinces and seven geological regions. Multivariable logistic regression was performed to obtain ORs and CIs of provinces/geological regions for CHD, stroke, and composite of both.

RESULTS

Age and sex standardized prevalence of CHD, stroke, and composite of both was, respectively, 4.59% (95% CI, 4.58 to 4.60), 1.79% (1.79 to 1.80), and 5.85% (5.84 to 5.86), in contrast to 0.60% of CHD, 0.80% of stroke, and 1.37% of composite of both in the general population in China. After adjustment for traditional risk factors, Northeast had the highest risks of CHD, stroke, and composite of both, and North had the second highest risks of CHD, stroke, and composite of both among the seven regions, both being higher than any other regions (all P values < 0.05). The ORs of Northeast vs Southwest were up to 2.60 (2.35 to 2.88) for CHD, 2.49 (2.15 to 2.88) for stroke, and 2.61 (2.38 to 2.86) for composite of both.

CONCLUSIONS

There were large variations in risks of CHD, stroke, and composite of both in T2DM in China with Northeast and North having the highest risks.

Metformin and lung cancer risk in patients with type 2 diabetes mellitus

This study evaluated whether metformin might reduce lung cancer risk. The reimbursement database of the Taiwan's National Health Insurance was used. A sample of 15414 never users and 280159 ever users of metformin (original sample) and a 1:1 matched-pairs of ever and never users (n=15414 in each group, matched sample) were recruited from patients with newly diagnosed type 2 diabetes mellitus during 1999-2005. They were followed until December 31, 2011. Cox regression incorporated with the inverse probability of treatment weighting using propensity score was used to estimate hazard ratios. Results showed that the respective incidence of lung cancer in ever and never users was 173.36 and 292.65 per 100000 person-years in the original sample; and was 211.71 and 292.65, respectively, in the matched sample. The overall hazard ratios (95% confidence intervals) of 0.586 (0.509-0.674) in the original sample and 0.717 (0.584-0.881) in the matched sample suggested a significantly lower risk among metformin users. Hazard ratios comparing the first (<22.60 months), second (22.60-46.67 months) and third (>46.67 months) tertile of cumulative duration of metformin use to never users was 1.163 (1.005-1.348), 0.612 (0.526-0.711) and 0.176 (0.148-0.210), respectively, in the original sample; and was 1.465 (1.131-1.897), 0.758 (0.566-1.016) and 0.228 (1.460-0.357) in the respective tertile of the matched sample. Sensitivity analyses after excluding patients with certain risk factors of cancer and subgroup analyses supported a favorable effect of metformin. In conclusion, metformin use may reduce lung cancer risk in patients with type 2 diabetes mellitus.

Metformin and esophageal cancer risk in Taiwanese patients with type 2 diabetes mellitus

This study evaluated whether metformin might reduce esophageal cancer risk. Patients with type 2 diabetes mellitus diagnosed during 1999–2005 were recruited from the reimbursement database of Taiwan's National Health Insurance. Those newly treated with metformin (n = 288013, “ever users of metformin”) or other antidiabetic drugs (n = 16216, “never users of metformin”) were followed until December 31, 2011. Sensitivity analyses were conducted in a matched-pair sample of 16216 never users and 16216 ever users. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. The risk associated with infection of Helicobacter pylori, Epstein-Barr virus, hepatitis B virus and hepatitis C virus was also evaluated. Results showed that the incidence of esophageal cancer in ever and never users was 25.03 and 50.87 per 100,000 person-years, respectively. The overall hazard ratio (95% confidence intervals) of 0.487 (0.347–0.684) suggested a significantly lower risk among metformin users. Hazard ratios comparing the first (< 21.47 months), second (21.47–46.00 months) and third (> 46.00 months) tertile of cumulative duration of metformin use to never users was 1.184 (0.834–1.680), 0.403 (0.276–0.588) and 0.113 (0.071–0.179), respectively. Infection of Helicobacter pylori (but not the other viral infections) significantly increased the risk, which could be ameliorated by metformin. Analyses in the matched sample consistently supported a protective role of metformin. In conclusion, metformin reduces esophageal cancer risk when the cumulative duration is more than approximately 2 years.

No Decreased Risk of Gastrointestinal Cancers in Users of Metformin in The Netherlands; A Time-Varying Analysis of Metformin Exposure

Previous studies on metformin use and gastrointestinal (GI) cancer risk have yielded inconclusive results on metformin's chemoprotective effects. We aimed to evaluate GI cancer risk in users of metformin in The Netherlands using a time-varying approach in a large population-based database. A cohort study was performed using the NCR-PHARMO database. Patients using ≥1 non-insulin antidiabetic drug (NIAD) during 1998 to 2011 were included (N = 57,621). Exposure to NIADs was modeled time-varyingly. Cox regression analysis estimated HRs of GI cancers in current metformin users versus current users of other NIADs. Covariables included age, sex, drugs known to impact cancer risk, history of hospitalization, and starting year of follow-up. A sensitivity analysis was performed, applying a new-user design. Current use of metformin was not associated with a decreased risk of GI cancer [HR, 0.97; 95% confidence interval (CI), 0.82-1.15] or specific GI cancer sites. The sensitivity analysis yielded comparable results. No decreasing trends were observed with increasing cumulative dose of metformin [HR 1.05, 95% CI, 0.85-1.28; HR 0.89, 95% CI, 0.73-1.10; HR 0.96, 95% CI, 0.77-1.19 for dose tertiles low (<405 g), medium (405-999 g), and high (≥999 g)]. In contrast, an increased risk of pancreatic cancer was found in current users of metformin plus insulin (HR, 4.90; 95% CI, 2.64-9.10). In conclusion, no decreased risk of GI cancer was found in current metformin users compared with current users of other NIADs. Variations in the exposure definition of metformin use may be one of the explanations of previously found reduced cancer risks in metformin users. Cancer Prev Res; 10(5); 290-7. ©2017 AACR.

Metformin may reduce oral cancer risk in patients with type 2 diabetes

BACKGROUND

Whether metformin use may affect the risk of oral cancer required further investigation.

METHODS

The reimbursement database of the National Health Insurance in Taiwan was used. Patients with type 2 diabetes mellitus at an onset age of 25-74 years during 1999-2005 and newly treated with either metformin (n = 288198, "ever users of metformin") or other antidiabetic drugs (n = 16263, "never users of metformin") were followed for at least 6 months for oral cancer until December 31, 2011. The treatment effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression adjusted for propensity score (PS) or incorporated with the inverse probability of treatment weighting (IPTW) using PS.

RESULTS

The respective numbers of incident oral cancer in ever users and never users were 1273 (0.44%) and 119 (0.73%), with respective incidences of 92.7 and 163.6 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) suggested a significantly lower risk [0.584 (0.483-0.707) for PS-adjusted model, and 0.562 (0.465-0.678) for IPTW model]. In tertile analyses, the PS-adjusted hazard ratios (95% confidence intervals) for the first (<21.5 months), second (21.5-45.9 months) and third (>45.9 months) tertile of cumulative duration were 1.403 (1.152-1.708), 0.557 (0.453-0.684) and 0.152 (0.119-0.194), respectively; and were 1.244 (1.024-1.511), 0.526 (0.429-0.645) and 0.138 (0.108-0.176), respectively, for IPTW.

CONCLUSIONS

Metformin may significantly reduce the risk of oral cancer, especially when the cumulative duration is more than 21.5 months.

Metformin reduces gastric cancer risk in patients with type 2 diabetes mellitus

This retrospective cohort study investigated whether metformin may reduce gastric cancer risk by using the reimbursement databases of the Taiwan's National Health Insurance. Patients with type 2 diabetes diagnosed during 1999-2005 and newly treated with metformin (n=287971, "ever users of metformin") or other antidiabetic drugs (n=16217, "never users of metformin") were followed until December 31, 2011. The effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Results showed that the respective numbers of incident gastric cancer in ever and never users were 759 (0.26%) and 89 (0.55%), with respective incidences of 55.26 and 122.53 per 100,000 person-years. The overall hazard ratio (95% confidence intervals) of 0.448 (0.359-0.558) suggested a significantly lower risk among ever users. In tertile analyses, hazard ratios (95% confidence intervals) for the first (＜21.47 months), second (21.47-45.97 months) and third (＞45.97 months) tertile of cumulative duration was 0.973 (0.773-1.224), 0.422 (0.331-0.537) and 0.120 (0.090-0.161), respectively, while compared to never users. In conclusion, metformin significantly reduces gastric cancer risk, especially when the cumulative duration is more than approximately 2 years.

Non-linear associations of risk factors with mild hypoglycemia among Chinese patients with type 2 diabetes

AIMS

The present study aimed to examine the nonlinear associations between risk factors and mild hypoglycemia in Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

From May 2013 to August 2013, we conducted a cross sectional survey of 6633 inpatients with T2DM and without severe hypoglycemia, aged 21-77 years, from 81 top tertiary hospitals in China. Mild hypoglycemia was defined as having hypoglycemia with symptoms in one month. Binary logistic regression analysis with restricted cubic splines was used to estimate odds ratio curves of non-linear risk factors for mild hypoglycemia.

RESULTS

Increasing body mass index was associated with decreasing risk of mild hypoglycemia in a linear manner while age, duration of diabetes, glycated hemoglobin (HbA1c), mean artery pressure and lipids were associated with mild hypoglycemia in non-linear manners. Age ≥40 years, duration ≥2 years, HbA1c ≥7.0-<11.5% (≥53-<102 mmol/mol), triglyceride ≥1.7-<3.6 mmol/L, low-density lipoprotein cholesterol (LDL-C) ≥2.6-<4.8 mmol/L, and high-density lipoprotein cholesterol (HDL-C) ≥1.2-<4.8 mmol/L were associated with increased risks of mild hypoglycemia.

CONCLUSIONS

Chinese T2DM patients with age≥40 years, duration of diabetes ≥2-<6 years, HbA1c ≥7.0-<11.5% (≥53-<102 mmol/mol), LDL-C ≥2.6-<4.8mmol/L, HDL-C ≥1.2-<4.8 mmol/L or triglyceride ≥1.7-<3.6 mmol/L were at particularly high risk for mild hypoglycemia.

Progression to treatment failure among Chinese patients with type 2 diabetes initiated on metformin versus sulphonylurea monotherapy--The Hong Kong Diabetes Registry

AIMS

To assess the development of treatment failure in Chinese patients with type 2 diabetes mellitus (T2DM) initiated on metformin or sulphonylurea (SU) monotherapy, with consideration of various potential sources of biases.

METHODS

A 1:1-matched new metformin and SU user cohort on immortal time and mean propensity score after multiple imputation was selected from a cohort of 5889 Chinese patients with T2DM. Treatment failure was defined as progression to (i) combination oral anti-hyperglycemia drug therapy, (ii) insulin use, or (iii) a treatment haemoglobin A1c (HbA1c) >7.5% (58 mmol/mol). Stratified Cox regression analysis on the matched pairs was employed to examine the associations between initial monotherapy and onset of treatment failure.

RESULTS

Of 554 new metformin and 840 new SU users, 380 were matched. During a median follow-up duration of 3 years, 173 (45.6%) metformin users and 220 (57.9%) SU users experienced treatment failure (annual failure rates of 15% and 19%, respectively). The median time from monotherapy starting to treatment failure was 3.0 [inter-quartile range (IQR): 1.8-5.4] years for metformin users, versus 1.8 (IQR: 0.9-4.1) years for SU users (p<0.001). Stratified Cox regression analysis showed significantly lower risk of treatment failure for metformin users (HR [95% CI], 0.62[0.47-0.81]; p<0.001). Consistent results were found in analyses based on traditional adjustment schemes with or without imputation.

CONCLUSIONS

By systematically incorporating new-user design, multiple imputation and matching methods, we found that Chinese patients with T2DM initiated on metformin monotherapy were associated with a significant delay in the onset of treatment failure compared to SU monotherapy.

Does Metformin Reduce Cancer Risks? Methodologic Considerations

The substantial burden of cancer and diabetes and the association between the two conditions has been a motivation for researchers to look for targeted strategies that can simultaneously affect both diseases and reduce their overlapping burden. In the absence of randomized clinical trials, researchers have taken advantage of the availability and richness of administrative databases and electronic medical records to investigate the effects of drugs on cancer risk among diabetic individuals. The majority of these studies suggest that metformin could potentially reduce cancer risk. However, the validity of this purported reduction in cancer risk is limited by several methodological flaws either in the study design or in the analysis. Whether metformin use decreases cancer risk relies heavily on the availability of valid data sources with complete information on confounders, accurate assessment of drug use, appropriate study design, and robust analytical techniques. The majority of the observational studies assessing the association between metformin and cancer risk suffer from methodological shortcomings and efforts to address these issues have been incomplete. Future investigations on the association between metformin and cancer risk should clearly address the methodological issues due to confounding by indication, prevalent user bias, and time-related biases. Although the proposed strategies do not guarantee a bias-free estimate for the association between metformin and cancer, they will reduce synthesis of and reporting of erroneous results.

Use of metformin and risk of kidney cancer in patients with type 2 diabetes

BACKGROUND

The anticancer effect of metformin has been reported in the literature but requires additional confirmation in epidemiologic studies. With respect to kidney cancer scarce data are available. This study investigates whether metformin use in patients with type 2 diabetes mellitus (T2DM) might affect kidney cancer risk.

METHODS

The reimbursement database of the National Health Insurance in Taiwan was used. T2DM patients aged ≥ 40 years and newly treated with either metformin (n=171,753, "ever users of metformin") or other antidiabetic drugs (n=75,499, "never users of metformin") within 1998-2002 were followed for at least 6 months for kidney cancer until 31 December 2009. The treatment effect was estimated by Cox regression using propensity score weighting by inverse probability of treatment weighting approach. Hazard ratios were estimated for ever versus never users, and for tertiles of cumulative duration of metformin therapy.

RESULTS

During follow-up, 917 ever users and 824 never users developed kidney cancer, with respective incidence of 80.09 and 190.30 per 100,000 person-years. The hazard ratio (95% confidence intervals) for ever versus never users is 0.279 (0.254-0.307); and is 0.598 (0.535-0.668), 0.279 (0.243-0.321) and 0.104 (0.088-0.124), respectively, for the first, second, and third tertile of cumulative duration of <14.5, 14.5-45.8 and >45.8 months. In subgroup analyses, the lower risk of kidney cancer associated with metformin use is consistently observed in both sexes, and in patients with or without concomitant use of other antidiabetic drugs.

CONCLUSION

Metformin use is associated with a decreased risk of kidney cancer in patients with T2DM.

Hypoglycemia and Comorbidities in Type 2 Diabetes

Hypoglycemia is one of the major barriers in optimizing glycemic control. In type 2 diabetes, hypoglycemia is associated with multiple morbidities (eg, myocardial ischemia, cardiac arrhythmia, stroke, dementia, psychosocial dysfunction, obesity, microvascular complications, cancer, and diseases of respiratory, digestive, and dermatological systems). Risk factors associated with hypoglycemia in patients with type 2 diabetes include old age, long disease duration, low body mass index, high baseline glycated hemoglobin (HbA1c), treatment with insulin and sulphonylurea, renal dysfunction, albuminuria, reduced level of low density lipoprotein cholesterol, low triglyceride and depression. There are considerable overlaps between phenotypes associated with severe hypoglycemia and all-site cancer suggesting that hypoglycemia may be a marker of vulnerability. In patients with severe hypoglycemia, comprehensive assessment is recommended to detect silent conditions, such as renal dysfunction, cancer, depression as well as review of treatment strategies including drug use to prevent morbidities and mortality.

Methodological challenges to control for immortal time bias in addressing drug effects in type 2 diabetes

There are multiple biases in using observational studies to examine treatment effects such as those from prevalent drug users, immortal time and drug indications. We used renin angiotensin system (RAS) inhibitors and statins as reference drugs with proven efficacies in randomized clinical trials (RCTs) and examined their effectiveness in the prospective Hong Kong Diabetes Registry using adjustment methods proposed in the literature. Using time-dependent exposures to drug treatments yielded greatly inflated hazard ratios (HR) regarding the treatment effects of these drugs for cardiovascular disease (CVD) in type 2 diabetes. These errors were probably due to changing indications to use these drugs during follow up periods, especially at the time of drug commencement making time-dependent analysis extremely problematic. Using time-fixed analysis with exclusion of immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of RAS inhibitors for CVD was comparable to that in RCT. The result supported the use of the Registry for performing pharmacoepidemiological analysis which revealed an attenuated low low-density lipoprotein cholesterol related cancer risk with RAS inhibitors. On the other hand, time-fixed analysis with including immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of statins for CVD was similar to that in the RCT. Our results highlight the complexity and difficulty in removing these biases. We call for validations of the methods to cope with immortal time and drug use indications before applying them to particular research questions, so to avoid making erroneous conclusions.

No reduced risk of overall, colorectal, lung, breast, and prostate cancer with metformin therapy in diabetic patients: database analyses from Germany and the UK

BACKGROUND

In observational studies, a lower cancer risk was reported for patients with diabetes using metformin. However, many of these studies had shortcomings like time-related biases. We aimed to compare the incidence rate of any cancer and some selected cancer sites in metformin, sulfonylurea, and insulin users and to reduce some major biases common in observational studies.

METHODS

In a retrospective database study, we used patient data from general practices throughout Germany and the UK. Eighty thousand two hundred and sixty-three patients aged 30-89 years at diagnosis of diabetes were observed for a mean follow-up of 4.8 years after the first antidiabetes medication. In Cox regression models adjusted for age, sex, country, metabolic factors, diabetes duration, medication, and comorbidity, patients who started using metformin were compared with those who started using sulfonylurea (or insulin) (intention-to-treat type analysis), and, additionally, patients with metformin monotherapy were compared with those with sulfonylurea (or insulin) monotherapy. The initial 12 months of follow-up after the first antidiabetes prescription were excluded.

RESULTS

Four thousand seven hundred seventy-nine (6.0%) incident cases of cancer were identified. Throughout all analyses, hazard ratios were close to the null for comparisons of metformin use with sulfonylurea and insulin use. For example, in intention-to-treat analyses comparing metformin with sulfonylurea use, hazard ratios were 1.05 (95%CI: 0.99-1.12) for any cancer, 1.05 (0.85-1.30) for colorectal, 1.04 (0.82-1.31) for lung, 1.03 (0.81-1.30) for breast, and 0.89 (0.73-1.08) for prostate cancer.

CONCLUSION

This study provides evidence that metformin has no protective effect on the incidence of cancer in persons with diabetes.

Drug-subphenotype interactions for cancer in type 2 diabetes mellitus

On the basis of data obtained from a prospective cohort of Chinese patients with type 2 diabetes mellitus (T2DM), we discuss cancer subphenotypes (risk factors) in patients with T2DM, which can lead to drug-cancer subphenotype interactions. These subphenotypes include HDL cholesterol levels <1.0 mmol/l, co-occurrence of LDL cholesterol levels <2.8 mmol/l and triglyceride levels <1.7 mmol/l, and co-occurrence of LDL cholesterol levels <2.8 mmol/l and albuminuria. The increased risk of cancer associated with low levels of HDL cholesterol, low LDL cholesterol levels plus low triglyceride levels, and low levels of LDL cholesterol plus albuminuria can be reduced by treatment with metformin, renin-angiotensin system (RAS) inhibitors and statins, respectively. Mechanistic studies support the hypothesis that dysregulation of the 5'-AMP-activated protein kinase pathway and crosstalk between the RAS and insulin-like growth factor 1-cholesterol pathways create a cancer-promoting milieu in patients with T2DM. These findings highlight that in Chinese individuals, multiple pathways are implicated in the link between T2DM and cancer, which can generate multiple subphenotypes as well as drug-subphenotype interactions.

Hyperglycemia and duration of diabetes as risk factors for abnormal lipids: a cross sectional survey of 19,757 patients with type 2 diabetes in China

PURPOSE

Type 2 diabetes (T2D) increases the risk of cardiovascular disease (CVD). Achieving glycated hemoglobin (HbA1c) below 7.0 % in newly diagnosed T2D reduced CVD risk. It is uncertain whether HbA1c below 7.0 % in T2D with varying duration of diabetes also reduced CVD risk. This study investigated the associations between hyperglycemia and abnormal lipid metabolism in patients with T2D.

METHODS

We conducted a survey of 19,757 outpatients with T2D who were 18 years of age or more and treated with oral antidiabetes drugs (OADs) alone or OADs combined with other drugs. The coverage rates of the 3A hospitals were 74.4 % for Beijing (n = 32), 76 % for Shanghai (n = 22), 55 % for Tianjin (n = 11) and 29.3 % for Guangzhou (n = 12). Abnormal lipids were defined as ≥2.6 mmol/L for low-density lipoprotein (LDL) cholesterol, ≤1.0 mmol/L in men and ≤1.3 mmol/L in women for high-density lipoprotein (HDL) cholesterol; ≥1.7 mmol/L for triglyceride. Logistic regression stratified on city and hospital was used to obtain odds ratio (OR) of hyperglycemia for abnormal lipids.

RESULTS

The patients had 4.0 (interquartile range 1.7-8.8) years of duration of diabetes. HbA1c ≥7.0 % was associated with increased risk of high LDL cholesterol (multivariable OR of ≥7.0 vs. <6.0 %:1.37, 95 % confidence interval 1.19-1.57). HbA1c ≥6.5 % was associated increased risk of high triglyceride. HbA1c was associated with low HDL cholesterol in a J-shaped manner, whereby HbA1c levels of <6.0 % as well as ≥6.5 % being associated with increased risk of low HDL cholesterol.

CONCLUSIONS

Hyperglycemia defined as HbA1c ≥7.0 % increased risk of high LDL cholesterol in T2D.

Renin angiotensin system inhibitors may attenuate low LDL cholesterol-related cancer risk in type 2 diabetes

BACKGROUND

In type 2 diabetes (T2D), copresence of low-density lipoprotein cholesterol (LDL-C) < 2.8 mmol/L with triglyceride < 1.7 mmol/L or with albuminuria synergistically increased cancer risk. We tested whether use of renin angiotensin system inhibitors attenuated the increased cancer risk associated with these two risk subphenotypes.

METHODS

A prospective cohort of 4307 patients with T2D enrolled from December 1996 to January 2005 was analysed using a new user cohort design. Cox model analysis was used to obtain hazard ratios and 95% confidence intervals. The study measured additive interactions between nonuse of renin angiotensin system inhibitors and low LDL-C plus low triglyceride or albuminuria for the risk of cancer. A positive interaction suggests a specific drug effect on the low LDL-C-related cancer risk.

RESULTS

During 18 769 person years of follow-up (median follow-up years: 4.44), 4.48% (n = 193) of patients developed cancer. Use of renin angiotensin system inhibitors was associated with reduced cancer risk among patients with copresence of low LDL-C plus low triglyceride or low LDL-C plus albuminuria but not in patients without these subphenotypes. In multivariable analysis, renin angiotensin system inhibitor usage attenuated the hazard ratio of copresence of low LDL-C plus low triglyceride versus lack of this subphenotype for cancer from 2.08 (95% CI: 1.25-3.47) to 1.13 (0.61-2.11) with significant additive interaction (p = 0.0225). Similarly, RAS inhibitor usage attenuated the hazard ratio of copresence of low LDL-C plus albuminuria versus lack of this subphenotype for cancer from 1.99 (95% CI: 1.12-3.56) to 0.82 (0.43-1.54) with significant additive interaction (p = 0.0009).

CONCLUSION

In T2D, renin angiotensin system inhibitor usage may specifically attenuate the low LDL-C-related cancer risk.

Additive effects of blood glucose lowering drugs, statins and renin-angiotensin system blockers on all-site cancer risk in patients with type 2 diabetes

BACKGROUND

Hyperglycemia is associated with increased risk of all-site cancer that may be mediated through activation of the renin-angiotensin-system (RAS) and 3-hydroxy-3-methyl-glutaryl-coenzyme-A-reductase (HMGCR) pathways. We examined the joint associations of optimal glycemic control (HbA1c <7%), RAS inhibitors and HMGCR inhibitors on cancer incidence in patients with type 2 diabetes.

METHODS

Patients with type 2 diabetes, with or without a history of cancer or prior exposure to RAS or HMGCR inhibitors at baseline were observed between 1996 and 2005. All patients underwent a comprehensive assessment at baseline and were followed until the censored date at 2005 or their death.

RESULTS

After a median follow-up period of 4.91 years (interquartile range, 2.81 to 6.98), 271 out of 6,103 patients developed all-site cancer. At baseline, patients with incident cancers were older, had longer disease duration of diabetes, higher alcohol and tobacco use, and higher systolic blood pressure and albuminuria, but lower triglyceride levels and estimated glomerular filtration rate (P <0.05). Patients who developed cancers during follow-up were less likely to have started using statins (22.5% versus 38.6%, P <0.001), fibrates (5.9% versus 10.2%, P = 0.02), metformin (63.8% versus 74.5%, P <0.001) or thiazolidinedione (0.7% versus 6.8%, P <0.001) than those who remained cancer-free. After adjusting for co-variables, new treatment with metformin (hazard ratio: 0.39; 95% confidence interval: 0.25, 0.61; P <0.001), thiazolidinedione (0.18; 0.04, 0.72; P = 0.015), sulphonylurea (0.44; 0.27, 0.73; P = 0.014), insulin (0.58; 0.38, 0.89; P = 0.01), statins (0.47; 0.31, 0.70; P <0.001) and RAS inhibitors (0.55; 0.39, 0.78; P <0.001) were associated with reduced cancer risk. Patients with all three risk factors of HbA1c ≥7%, non-use of RAS inhibitors and non-use of statins had four-fold adjusted higher risk of cancer than those without any risk factors (incidence per 1,000-person-years for no risk factors: 3.40 (0.07, 6.72); one risk factor: 6.34 (4.19, 8.50); two risk factors: 8.40 (6.60, 10.20); three risk factors: 13.08 (9.82, 16.34); P <0.001).

CONCLUSIONS

Hyperglycemia may promote cancer growth that can be attenuated by optimal glycemic control and inhibition of the RAS and HMGCR pathways.

Metformin may reduce breast cancer risk in Taiwanese women with type 2 diabetes

Whether metformin therapy affects breast cancer risk in Asian patients with type 2 diabetes mellitus (T2DM) has not been investigated. The reimbursement databases of Taiwanese female patients with a new diagnosis of T2DM between 1998 and 2002 (n = 476,282) were retrieved from the National Health Insurance for follow-up of breast cancer until the end of 2009. Metformin was treated as a time-dependent variable; and of these patients, 285,087 were never-users and 191,195 were ever-users. A time-dependent approach was used to calculate breast cancer incidence and estimate hazard ratios by Cox regression for ever-users, never-users, and subgroups of metformin exposure (tertiles of cumulative duration and cumulative dose). During follow-up, 2,412 (1.26 %) metformin ever-users and 9,322 (2.10 %) never-users developed breast cancer, representing an incidence of 201.08 and 535.88 per 100,000 person-years, respectively. The overall multivariable-adjusted hazard ratio (95 % confidence intervals) for ever- versus never-users was 0.630 (0.597-0.665). The multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative duration of metformin therapy were 1.122 (1.043-1.207), 0.754 (0.692-0.820), and 0.280 (0.253-0.310), respectively, (P-trend <0.0001); and 1.099 (1.021-1.182), 0.664 (0.611-0.723), and 0.311 (0.281-0.344), respectively, (P-trend <0.0001), for cumulative dose of metformin. Metformin use is associated with a decreased risk of breast cancer.

Metformin may reduce bladder cancer risk in Taiwanese patients with type 2 diabetes

Whether metformin therapy affects bladder cancer risk in patients with type 2 diabetes mellitus (T2DM) has not been extensively investigated. The reimbursement databases of all Taiwanese patients with a new diagnosis of T2DM between 1998 and 2002 (n = 940,708) were retrieved from the National Health Insurance for follow-up of bladder cancer up to the end of 2009. Metformin was treated as a time-dependent variable, and of these patients, 532,519 were never-users and 408,189 were ever-users of metformin. A time-dependent approach was applied in the calculation of bladder cancer incidence and in the estimation of hazard ratios by Cox regression for ever-users, never-users, and subgroups of metformin exposure (using tertile cutoffs of cumulative duration of therapy and cumulative dose). During the study period, 1,847 (0.45%) metformin ever-users and 6,213 (1.17%) metformin never-users developed bladder cancer, representing an incidence of 72.03 and 189.22 per 100,000 person-years, respectively. The age-sex-adjusted and multivariable-adjusted hazard ratios (95% confidence intervals) for ever- versus never-users were 0.382 (0.360-0.405) and 0.600 (0.564-0.638), respectively. The multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative duration of metformin therapy were 1.034 (0.954-1.120), 0.696 (0.632-0.766), and 0.258 (0.229-0.291), respectively (P trend <0.0001). Similarly, the multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative dose of metformin were 0.997 (0.920-1.080), 0.615 (0.559-0.677), and 0.285 (0.253-0.321), respectively (P trend <0.0001). This study suggests that metformin use is associated with a decreased risk of bladder cancer in patients with T2DM.

Severe hypoglycemia identifies vulnerable patients with type 2 diabetes at risk for premature death and all-site cancer: the Hong Kong diabetes registry

OBJECTIVE We examined the associations of clinical profiles in type 2 diabetic patients who developed severe hypoglycemia and their clinical outcomes, including death and all-site cancer. RESEARCH DESIGN AND METHODS A consecutive cohort of 8,767 type 2 diabetic patients with and without severe hypoglycemia in the 12 months before enrollment were recruited between 1995 and 2007, with follow-up until 2009. Severe hypoglycemia was defined by ICD-9 codes as hospitalizations resulting from hypoglycemia. Cox proportional hazards regression was used to calculate the hazard ratio (HR) and 95% CIs of clinical factors collected at enrollment for severe hypoglycemia. RESULTS In this cohort, mean age was 57.4 (SD 13.2) years and median disease duration of diabetes was 5 (interquartile range [IQR] 1-11) years. During a median follow-up of 6.71 (IQR 3.47-10.38) years, 235 patients had severe hypoglycemia (incidence 3.96 [95% CI 3.45-4.46] per 1,000 patient-years). At enrollment, patients with and without severe hypoglycemia had similar cancer rates. During follow-up, patients with severe hypoglycemia had a higher incidence of all-site cancer (13.4 vs. 6.4%, P < 0.0001) and mortality (32.8 vs. 11.2%, P < 0.0001) than those without severe hypoglycemia. After adjusting for confounders, old age, low BMI, high glycated hemoglobin, low triglyceride (TG), low LDL cholesterol (LDL-C), albuminuria, and chronic kidney disease were independent predictors for severe hypoglycemia. CONCLUSIONS In type 2 diabetes, severe hypoglycemia is associated with advanced age, renal dysfunction, poor glycemic control, and cancer subphenotypes (low BMI, low LDL-C, and low TG).

Tourniquet use for peripheral vascular injuries in the civilian setting

BACKGROUND

Haemorrhage in peripheral vascular injuries may cause life-threatening exsanguination. Tourniquets are used extensively by the military, with increased interest in the civilian setting to prevent deaths. This is a retrospective study of trauma patients at two large Canadian trauma centres with arterial injury after isolated extremity trauma. We hypothesized that tourniquet use may decrease mortality rate and transfusion requirements if applied early.

METHODS

The study group was all adult patients at two Level 1 Trauma Centres in two Canadian cities in Canada, who had arterial injuries from extremity trauma. The study period was from January 2001 to December 2010. We excluded patients with significant associated injuries. The intervention in this study was prehospital tourniquet use. The main outcome was in-hospital mortality. Secondary outcomes were length of stay, compartment syndrome, amputation, and blood product transfusion.

RESULTS

190 patients were included in the study, and only 4 patients had a prehospital tourniquet applied. They arrived directly from the scene of injury, had improvised tourniquets by police or bystanders, and showed a trend to be more hypotensive and acidotic. Four other patients had tourniquets applied in the trauma bay within 1h of injury. There were no differences in age, sex, injury severity or physiologic presentation between patients who had an early tourniquet applied and those who died without a tourniquet. However, six patients died without a tourniquet, and all bled to death. Of the eight patients who had early tourniquets applied, none died.

CONCLUSIONS

Tourniquets may prevent exsanguination in the civilian setting for patients suffering either blunt or penetrating trauma to the extremity. Future studies will help determine the utility of deploying tourniquets in the civilian setting, given the rarity of exsanguinating haemorrhage from isolated extremity trauma in this setting.

Metformin exposure and disseminated disease in patients with colorectal cancer

BACKGROUND

Preclinical evidence suggests a role for metformin in inhibiting tumour dissemination and metastasis. Previous studies have identified associations between metformin exposure and improved colorectal cancer survival. This study aimed to examine associations between metformin exposure and the odds of presenting with disseminated disease among colorectal cancer patients.

METHODS

Colorectal cancer patients diagnosed 2001-2006 were identified from the National Cancer Registry Ireland. A linked national pharmacy claims database was used to determine exposure to anti-diabetic medications prior to diagnosis. Multivariate logistic regression was used to estimate odds ratios (OR) with 95% confidence intervals (CI) for associations between metformin use (versus non-metformin anti-diabetic drugs) and odds of presenting with disseminated disease (lymph node positive/metastatic). Analyses were stratified by anti-diabetic drug co-prescription and intensity of metformin exposure.

RESULTS

The study population included 241 metformin-exposed diabetics, 129 non-metformin-exposed diabetics, and 4277 non-diabetic patients. In multivariate analysis, odds of disseminated disease were lower in metformin-exposed diabetics, compared with non-metformin-exposed diabetics, though not statistically significant (OR=0.66, 95% CI 0.39-1.12). In analyses stratified by metformin dosing intensity and anti-diabetic drug co-prescription, the odds were further from unity and approached significance in diabetics with high intensity, exclusive metformin use (OR=0.52, 95% CI 0.25-1.10).

CONCLUSIONS

While overall there was no statistically significant association between metformin exposure and disseminated colorectal cancer at diagnosis, there was a suggestion that high intensity, exclusive metformin use may be associated with reduced odds of disseminated disease. The number of patients in these subgroup analyses was small, and further investigation in larger studies is warranted.

A review on thiazolidinediones and bladder cancer in human studies

There is a concern of an increased risk of bladder cancer associated with the use of thiazolidinediones, a class of oral glucose-lowering drugs commonly used in patients with type 2 diabetes with a mechanism of improving insulin resistance. Human studies on related issues are reviewed, followed by a discussion on potential concerns on the causal inference in current studies. Pioglitazone and rosiglitazone are discussed separately, and findings from different geographical regions are presented. Randomized controlled trials designed for primarily answering such a cancer link are lacking, and evidence from clinical trials with available data for evaluating the association may not be informative. Observational studies have been reported with the use of population-based administrative databases, single-hospital records, drug adverse event reporting system, and case series collection. Meta-analysis has also been performed by six different groups of investigators. These studies showed a signal of higher risk of bladder cancer associated with pioglitazone, especially at a higher cumulative dose or after prolonged exposure; however, a weaker signal or null association is observed with rosiglitazone. In addition, there are some concerns on the causal inference, which may be related to the use of secondary databases, biases in sampling, differential detection, and confounding by indications. Lack of full control of smoking and potential biases related to study designs and statistical approaches such as prevalent user bias and immortal time bias may be major limitations in some studies. Overlapping populations and opposing conclusions in studies using the same databases may be of concern and weaken the reported conclusions of the studies. Because randomized controlled trials are expensive and unethical in providing an answer to this cancer issue, observational studies are expected to be the main source in providing an answer in the future. Furthermore, international comparison studies using well-designed and uniform methodology to clarify the risk in specific sexes, ethnicities, and other subgroups and to evaluate the interaction with other environmental risk factors or medications will be helpful to identify patients at risk.

A cohort study of metformin exposure and survival in patients with stage I-III colorectal cancer

BACKGROUND

Preclinical evidence suggests a beneficial effect of metformin in colorectal cancer. This study aimed to investigate associations between metformin exposure and colorectal cancer-specific survival using population-level data.

METHODS

Adult patients with stage I-III colorectal cancer diagnosed from 2001 to 2006 were identified from the National Cancer Registry Ireland. Use of metformin and other antidiabetic medications was determined from a linked national prescription claims database. Multivariate Cox regression was used to estimate hazard ratios (HR) with 95% confidence intervals (CI) for associations between prediagnostic metformin exposure (versus nonmetformin antidiabetic drugs) and colorectal cancer-specific mortality. Models were stratified by antidiabetic drug coprescription and intensity of metformin exposure.

RESULTS

The cohort included 207 diabetics who received metformin, 108 diabetics not exposed to metformin, and 3,501 nondiabetic patients. In multivariate analyses, a nonsignificant reduction in colorectal cancer-specific mortality was observed for metformin-exposed patients relative to other treated diabetics (HR, 0.61; 95% CI, 0.37-1.01). In stratified analyses, no significant association was observed for patients receiving low-intensity metformin or metformin in combination with other antidiabetic drugs. High-intensity exclusive metformin use was associated with a significant reduction in colorectal cancer-specific mortality (HR, 0.44; 95% CI, 0.20-0.95).

CONCLUSIONS

Significant associations between metformin exposure and colorectal cancer-specific mortality were observed only for high-intensity exclusive metformin use in the diabetic cohort.

IMPACT

This study provides moderate evidence of an association between metformin exposure and improved colorectal cancer survival in a diabetic population. Additional studies in larger cohorts, with detailed information on diabetes severity, are required to confirm these results.

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

OBJECTIVE

To estimate the prevalence of diagnosed cancer according to duration of diagnosed diabetes and current insulin use among U.S. adults with diagnosed diabetes.

RESEARCH DESIGN AND METHODS

We analyzed data from 25,964 adults aged ≥ 18 years with diagnosed diabetes who participated in the 2009 Behavioral Risk Factor Surveillance System.

RESULTS

After adjustment for potential confounders, we found that the greater the duration of diagnosed diabetes, the higher the prevalence of diagnosed cancers (P < 0.0001 for linear trend). Among adults with diagnosed type 2 diabetes, the prevalence estimate for cancers of all sites was significantly higher among men (adjusted prevalence ratio 1.6 [95% CI 1.3-1.9]) and women (1.8 [1.5-2.1]) who reported being diagnosed with diabetes ≥ 15 years ago than among those reporting diabetes diagnosis <15 years ago. The prevalence estimate for cancers of all sites was ~1.3 times higher among type 2 diabetic adults who currently used insulin than among those who did not use insulin among both men (1.3 [1.1-1.6]) and women (1.3 [1.1-1.5]).

CONCLUSIONS

Our results suggest that there is an increased burden of diagnosed cancer among adults with a longer duration of diagnosed diabetes and among type 2 diabetic adults who currently use insulin.

Enhancers and attenuators of risk associations of chronic hepatitis B virus infection with hepatocellular carcinoma in type 2 diabetes

Chronic hepatitis B virus (HBV) infection promotes hepatocellular carcinoma (HCC) risk. In type 2 diabetes (T2D), use of insulin and statins was associated with reduced cancer risk while co-presence of low LDL cholesterol (LDLC <2.8 mmol/l) plus low triglyceride (TG; <1.7 mmol/l) increased cancer risk. There is experimental evidence showing that insulin insufficiency might promote HCC. In this study, we examined whether this lipid subphenotype and use of insulin or statins might modify the promoting effect of chronic HBV infection (indicated by the presence of hepatitis B surface antigen) on HCC. We analyzed data of 1319 T2D patients enrolled into the Hong Kong Diabetes Registry from December 1996 to January 2005 and followed up to 2005. Additive interaction was estimated using relative excess risk due to interaction and attributable proportion due to interaction. During 5782 person-years of follow-up, 1.74% (n=23) of patients developed HCC (incidence, 3.98; 95% confidence interval, 2.36-5.60/1000 person-years). HbA1c ≥7.0% and the lipid phenotype (LDLC <2.8 mmol/l plus TG <1.7 mmol/l) increased the hazard ratios (HRs) of chronic HBV infection for HCC from 3.74 to 74.96 and from 11.01 to 89.82 respectively with significant interactions. Use of insulin or statins decreased the HRs from 37.51 to 5.87 and from 64.94 to 16.99 respectively with significant interactions (all P values <0.05). These findings support our hypothesis that hyperglycemia and co-presence of low LDLC plus low TG might enhance, while insulin or statin usage might attenuate the promoting effect of chronic HBV infection on HCC in T2D.

Statins and the risk of gastric cancer in diabetes patients

Background

Several studies have suggested a cancer risk reduction in statin users although the evidence remains weak for stomach cancer. The purpose of this study was to use an exact-matching case–control design to examine the risk of gastric cancer associated with the use of statins in a cohort of patients with diabetes.

Methods

Cases were defined as patients with incident gastric cancer identified by International Classification of Diseases 16.0 ~ 16.9 recorded at Samsung Medical Center database during the period of 1999 to 2008, at least 6 months after the entry date of diabetes code. Each gastric cancer case patient was matched with one control patient from the diabetes patient registry in a 1:1 fashion, blinded to patient outcomes.

Results

A total of 983 cases with gastric cancer and 983 controls without gastric cancer, matched by age and sex, were included in the analysis. The presence of prescription for any statin was inversely associated with gastric cancer risk in the unadjusted conditional logistic regression model (OR: 0.18; 95% CI: 0.14 – 0.24; P < .0001). Multivariate analysis using conditional logistic regression with Bonferroni’s correction against aspirin indicated a significant reduction in the risk of gastric cancer in diabetes patients with statin prescriptions (OR: 0.21; 95% CI: 0.16 – 0.28; P < .0001). After adjustment for aspirin use, a longer duration of statin use was associated with reduced risk of gastric cancer, with statistical significance (P<.0001).

Conclusions

A strong inverse association was found between the risk of gastric adenocarcinoma and statin use in diabetic patients.

Synergistic effects of low LDL cholesterol with other factors for the risk of cancer in type 2 diabetes: the Hong Kong Diabetes Registry

We have reported associations of cancer with low triglyceride and high high-density lipoprotein cholesterol (HDL-C) as well as co-presence of low low-density lipoprotein cholesterol (LDL-C) and albuminuria in type 2 diabetes (T2D). This analysis aims to test (1) whether low LDL-C and low triglyceride have synergistic effects to increase cancer risk in T2D and (2) whether high HDL-C enhances the effect of co-presence of low LDL-C and albuminuria on cancer risk. A prospective cohort of patients with T2D, established within the Prince of Wales Hospital, was used in the analysis. A total of 3,476 T2D patients in Hong Kong enrolled between 1996 and 2005, free of cancer at enrolment and not using statins or fibrates within 2.5 years before enrolment and during follow-up, were followed until 2005. The study measured additive interactions of low LDL-C with other factors for cancer using relative excess risk due to interaction (RERI) and attributable proportion due to interaction (AP). A statistically significant RERI > 0 or AP > 0 indicates additive interaction. During 5.11 years of follow-up, 199 patients developed cancer. Co-presence of triglyceride <1.70 mmol/L and LDL-C < 2.80 mmol/L was associated with increased cancer risk (multivariable hazard ratio [HR]:2.13, P = 0.0008) with significant interaction. Co-presence of HDL-C ≥ 1.30 mmol/L and LDL-C < 2.80 mmol/L plus albuminuria was also associated with increased cancer risk (HR: 3.84, P < 0.0001) with significant interaction. In T2D, low triglyceride may potentiate cancer risk associated with low LDL-C while high HDL-C enhances the synergistic effect of low LDL-C with albuminuria towards increased cancer risk.

Diabetes, insulin and cancer risk

There is a consensus that both type 1 and type 2 diabetes are associated with a spectrum of cancers but the underlying mechanisms are largely unknown. On the other hand, there are ongoing debates about the risk association of insulin use with cancer. We have briefly reviewed recent related research on exploration of risk factors for cancer and pharmacoepidemiological investigations into drug use in diabetes on the risk of cancer, as well as the current understanding of metabolic pathways implicated in intermediary metabolism and cellular growth. Based on the novel findings from the Hong Kong Diabetes Registry and consistent experimental evidence, we argue that use of insulin to control hyperglycemia is unlikely to contribute to increased cancer risk and that dysregulations in the AMP-activated protein kinase pathway due to reduced insulin action and insulin resistance, the insulin-like growth factor-1 (IGF-1)-cholesterol synthesis pathway and renin-angiotensin system, presumably due to reduced insulin secretion and hyperglycemia, may play causal roles in the increased risk of cancer in diabetes. Further exploration into the possible causal relationships between abnormalities of these pathways and the risk of cancer in diabetes is warranted.