Glucose-lowering therapies and cancer risk: the trials and tribulations of trials and observations

The influence of diabetes and antidiabetic medications on the risk of pancreatic cancer: a nationwide population-based study in Korea

This study investigated the effects of diabetes and antidiabetic medications on the risk of pancreatic cancer(PaC). We extracted data on Koreans with newly diagnosed diabetes and selected age- and sex-matched controls provided by the National Health Insurance Corporation. Incident PaC was defined as a new registration in the Korea Central Cancer Registry under ICD-10 C25 with admission history until 2015. During 19,429,617.1 person-years, 8,589 PaCs were identified in 1,005,409 subjects for diabetes group and 4,021,636 subjects for control group. The diabetes group showed more than a two-fold risk for PaC compared with the control group. Among antidiabetic medications, metformin, thiazolidinedione, and dipeptidyl peptidase-4 inhibitor exposure was associated with decreased risk for future PaC(hazard ratio[95% confidence interval] = 0.86[0.77–0.96], 0.82[0.68–0.98], 0.57[0.51–0.64], respectively), whereas sulfonylurea and insulin exposure was related to increased risk(hazard ratio[95% CI] = 1.73[1.57–1.91], 2.86[1.43–5.74], respectively) compared to subjects with no drug exposure. Moreover, subjects with dual exposure history to metformin plus thiazolidinedione or metformin plus dipeptidyl peptidase-4 inhibitor had a lower risk of PaC compared to metformin-only treated subjects. In conclusion, Korean adults with diabetes are at higher risk of PaC compared with nondiabetic individuals, and this risk may be modified by antidiabetic medications.

Anti-diabetic medications do not influence risk of lung cancer in patients with diabetes mellitus: a systematic review and meta-analysis

OBJECTIVES

Several preclinical and observational studies have shown that anti-diabetic medications (ADMs) may modify the risk of lung cancer. We performed a systematic review and meta-analysis evaluating the effect of metformin, sulfonylureas (SUs), thiazolidinediones (TZDs), and insulin on the risk of lung cancer in patients with diabetes mellitus (DM).

MATERIALS AND METHODS

We conducted a systematic search of Pubmed and Web of Science, up to August 20, 2013. We also searched the Conference Proceedings Citation Index (CPCI) and China National Knowledge Infrastructure (CNKI) for abstracts from major meetings. Fixed or random effect pooled measures were selected based on heterogeneity among studies, which was evaluated using Q test and the I2 of Higgins and Thompson. Meta-regression was used to explore the sources of between-study heterogeneity. Publication bias was analyzed by Begg's funnel plot and Egger's regression test. Associations were assessed by odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

A total of 15 studies (11 cohort, 4 case-control) were included in this meta-analysis. In observational studies no significant association between metformin (n=11 studies; adjusted OR=0.99, 95%CI: 0.87-1.12), SUs (n=5 studies; adjusted OR=0.98, 95%CI: 0.79-1.22), or TZDs (n=7 studies; adjusted OR=0.92, 95%CI: 0.75-1.13), insulin (n=6 studies; adjusted OR=1.13, 95%CI: 0.79-1.62) use and risk of developing lung cancer was noted. There was considerable inherent heterogeneity between studies not explained by study design, setting, or location.

CONCLUSIONS

Meta-analysis of existing studies does not support a protective or harmful association between ADMs use and risk of lung cancer in patients with DM. There was considerable heterogeneity across studies, and future, well-designed, prospective studies would be required for better understanding of any association.

Differential pathway coupling of the activated insulin receptor drives signaling selectivity by XMetA, an allosteric partial agonist antibody

The monoclonal antibody XMetA is an allosteric partial agonist of the insulin receptor (IR), which activates the metabolic Akt kinase signaling pathway while having little or no effect on the mitogenic extracellular signal-regulated kinase (ERK) signaling pathway. To investigate the nature of this selective signaling, we have conducted a detailed investigation of XMetA to evaluate specific phosphorylation and activation of IR, Akt, and ERK in Chinese hamster ovary cell lines expressing either the short or long isoform of the human IR. Insulin activated both pathways, but the phosphorylation of Akt was more sensitive to the hormone than the phosphorylation of ERK. Maximally effective concentrations of XMetA elicited phosphorylation patterns similar to 40-100 pM insulin, which were sufficient for robust Akt phosphorylation, but had little effect on ERK phosphorylation. These data indicate that the preferential signaling of XMetA is due to an innate difference in pathway sensitivity of Akt versus ERK responses to IR activation and partial agonism by XMetA, rather than a separate pathway-biased mechanism. The metabolic selectivity of partial IR agonists like XMetA, if recapitulated in vivo, may be a desirable feature of therapeutic agents designed to regulate blood glucose levels while minimizing undesirable outcomes of excessive IR mitogenic activation.

Anti-diabetic medications and the risk of hepatocellular cancer: a systematic review and meta-analysis

Several preclinical and observational studies have shown that anti-diabetic medications (ADMs) can modify the risk of hepatocellular cancer (HCC) in patients with diabetes mellitus (DM). We performed a systematic review and meta-analyses of studies evaluating the effect of metformin, thiazolidinediones (TZDs), sulfonylureas, and/or insulin on the risk of HCC. We conducted a systematic search of Medline, EMBASE, and Web of Science up to August 2012. Studies were included if they (1) evaluated and clearly defined exposure to metformin, TZDs, sulfonylureas, and/or insulin, (2) reported HCC outcomes in patients with DM, and (3) reported relative risks or odds ratio (OR) or provided data for their estimation. Summary OR estimates with 95% confidence intervals (CIs) were estimated using the random-effects model. Ten studies reporting 22,650 cases of HCC in 334,307 patients with type 2 DM were included in the analysis. Meta-analysis of observational studies showed a 50% reduction in HCC incidence with metformin use (n=8 studies; OR 0.50, 95% CI 0.34-0.73), 62% and 161% increase in HCC incidence with sulfonylurea (n=8 studies; OR 1.62, 95% CI 1.16-2.24) or insulin use (n=7; OR 2.61, 95% CI 1.46-4.65), respectively. TZDs did not modify the risk of HCC (n=4; OR 0.54, 95% CI 0.28-1.02). There was considerable heterogeneity across studies, which was partly explained by study setting, location, and whether the studies adjusted for the concomitant use of other ADMs. Post-hoc analysis of randomized controlled trials did not reveal any significant association between ADM use and risk of HCC. ADMs may modify the risk of HCC in patients with DM, especially in the Western population. However, the effect of each individual agent should be interpreted with caution owing to inherent cancer-modifying effect of the comparator group.

Anti-diabetic medications and risk of pancreatic cancer in patients with diabetes mellitus: a systematic review and meta-analysis

OBJECTIVES

Several preclinical and observational studies have shown that anti-diabetic medications (ADMs) may modify the risk of pancreatic cancer (PaC). We performed a systematic review and meta-analysis evaluating the effect of metformin, sulfonylureas (SUs), thiazolidinediones (TZDs), and insulin on the risk of PaC in patients with diabetes mellitus (DM).

METHODS

We conducted a systematic search of Medline, EMBASE, and Web of Science, up to June 2012, and published abstracts from major gastroenterology and oncology meetings from 2003 to 2012. Studies were included if they (1) evaluated and clearly defined exposure to metformin, SU, TZDs, and/or insulin, (2) reported PaC outcomes in patients with DM and (3) reported relative risks or odds ratio (OR) or provided data for their estimation. Summary OR estimates with 95% confidence intervals (CIs) were estimated using the random-effects model.

RESULTS

Eleven studies (6 cohort, 3 case-control, and 2 randomized controlled trials (RCTs)) reported 1770 cases of PaC in 730,664 patients with DM. Meta-analysis of observational studies showed no significant association between metformin (n=9 studies; adjusted OR 0.76, 95% CI 0.57-1.03, P=0.073), insulin (n=7 studies; adjusted OR 1.59, 95% CI 0.85-2.96, P=0.144), or TZD (n=4 studies; adjusted OR 1.02, 95% CI 0.81-1.30, P=0.844) use and risk of developing PaC. Use of SU was associated with a 70% increase in the odds of PaC (n=8 studies; adjusted OR 1.70, 95% CI 1.27-2.28, P<0.001). There was considerable inherent heterogeneity between studies not explained by study design, setting, or comparator drug and is likely related to confounding by indication and reverse causality. The pooled analyses of the two RCTs were underpowered and provided non-significant results with wide, non-informative 95% CIs.

CONCLUSIONS

Although SU seems to be associated with increased risk of PaC, meta-analysis of existing studies does not support a protective or harmful association between ADM use and risk of PaC in patients with DM. There was considerable heterogeneity across studies, and future, well-designed, prospective studies would be required to understand this association better.

Diabetes, glucose control, glucose lowering medications, and cancer risk: a 10-year population-based historical cohort

Background

Both diabetes and glucose-lowering medications have been associated with an increased risk of cancer incidence. This study will compare cancer incidence rates in individuals with and without diabetes; and will investigate, in individuals with diabetes, an association between glucose control and cancer incidence; and between the use of specific glucose-lowering medications, as well as no drug exposure, and cancer incidence.

Methods/design

This is a population based historical cohort study of all individuals aged 21 years or older (about 2,300,000) who were insured by Clalit Health Services, the largest health maintenance organization in Israel during a ten-year study period. Four study groups will be established according to the status of diabetes and cancer at study entry, Jan 1, 2002: cancer free, diabetes free; cancer free, diabetes prevalent; cancer prevalent, diabetes free; and cancer prevalent, diabetes prevalent. Individuals without diabetes at study entry will be followed for diabetes incidence, and all four groups will be followed for specific cancer incidence, including second primary neoplasms. Glucose control will be assessed by HbA1c and by fasting plasma glucose levels. Time dependent regression models for cancer incidence will account for glucose-lowering medications as they are added and changed over the follow-up period. A large number of demographic and clinical variables will be considered, including: age, gender, BMI, smoking status, concomitant medications, glucose control (assessed by HbA1c and by fasting plasma glucose) and cancer screening tests.

Discussion

Strengths of this study include the large population; high quality comprehensive data; comparison to individuals without diabetes, and to those with diabetes but not treated with glucose-lowering medications; and the extensive range of variables available for analysis. The great increases in diabetes prevalence and in treatment options render this study particularly relevant and timely. The Israeli national healthcare system, characterized by high standard and uniform healthcare, offers an advantageous environment for its conduct.

Diabetes and cancer (1): evaluating the temporal relationship between type 2 diabetes and cancer incidence

Substantial evidence suggests that people with type 2 diabetes have an increased risk of developing several types of cancers. These associations may be due to a number of direct and indirect mechanisms. Observational studies of these associations, including the potential role for glucose-lowering therapy, are being increasingly reported, but face a number of methodological challenges. This paper is the first of two review papers addressing methodological aspects underpinning the interpretations of links between diabetes and cancer, and suggests potential approaches to study designs to be considered in observational studies. This paper reviews factors related to cancer incidence in the diabetic population; the second paper relates to studies of cancer mortality.

Serial glycosylated hemoglobin levels and risk of colorectal neoplasia among patients with type 2 diabetes mellitus

BACKGROUND

Hyperglycemia may increase the risk of colorectal neoplasia by serving as an energy source for neoplastic growth. We sought to determine whether glycemic control measured by serial hemoglobin A1c (HbA1c) was associated with the risk of colorectal adenoma.

METHODS

Among a cohort of patients with type 2 diabetes mellitus who received health care within the Kaiser Permanente Northern California from 1994 to 2005, we conducted 2 case-control analyses. Cases had at least 1 colorectal adenoma identified at either colonoscopy (analysis 1) or sigmoidoscopy (analysis 2). Controls had no colorectal neoplasia identified at the corresponding endoscopic examination. Serial HbA1c levels between the cases and the controls were compared using a longitudinal model.

RESULTS

Case-control analysis 1 included 4,248 patients, of whom 1,296 (31%) had at least 1 adenoma. The adjusted mean HbA1c levels among those without any adenomas was 8.20% versus 8.26% among those with at least 1 adenoma, a difference of 0.06% (95% CI = -0.02 to 0.14, P = 0.16). Case-control analysis 2 included 9,813 patients, of whom 951 (10%) had at least 1 distal adenoma. The adjusted mean HbA1c levels among those without any distal adenomas was 8.32% versus 8.37% among those with at least 1 distal adenoma, a difference of 0.05% (95% CI = -00.04 to 0.14, P = 0.25). The results were similar for advanced adenomas.

CONCLUSIONS

Glycemic control was not associated with the risk of colorectal adenoma among diabetic persons.

IMPACT

These results would suggest that glycemic control is unlikely to confound the reported association between diabetes medications and the risk of colorectal cancer.