Personal history of diabetes, genetic susceptibility to diabetes, and risk of brain glioma: a pooled analysis of observational studies

The Influence of Ethnicity on Survival from Malignant Primary Brain Tumours in England: A Population-Based Cohort Study

BACKGROUND

In recent years, the completeness of ethnicity data in the English cancer registration data has greatly improved. Using these data, this study aims to estimate the influence of ethnicity on survival from primary malignant brain tumours.

METHODS

Demographic and clinical data on adult patients diagnosed with malignant primary brain tumour from 2012 to 2017 were obtained (n = 24,319). Univariate and multivariate Cox proportional hazards regression analyses were used to estimate hazard ratios (HR) for the survival of the ethnic groups up to one year following diagnosis. Logistic regressions were then used to estimate odds ratios (OR) for different ethnic groups of (1) being diagnosed with pathologically confirmed glioblastoma, (2) being diagnosed through a hospital stay that included an emergency admission, and (3) receiving optimal treatment.

RESULTS

After an adjustment for known prognostic factors and factors potentially affecting access to healthcare, patients with an Indian background (HR 0.84, 95% CI 0.72-0.98), Any Other White (HR 0.83, 95% CI 0.76-0.91), Other Ethnic Group (HR 0.70, 95% CI 0.62-0.79), and Unknown/Not Stated Ethnicity (HR 0.81, 95% CI 0.75-0.88) had better one-year survivals than the White British Group. Individuals with Unknown ethnicity are less likely be diagnosed with glioblastoma (OR 0.70, 95% CI 0.58-0.84) and less likely to be diagnosed through a hospital stay that included an emergency admission (OR 0.61, 95% CI 0.53-0.69).

CONCLUSION

The demonstrated ethnic variations associated with better brain tumour survival suggests the need to identify risk or protective factors that may underlie these differences in patient outcomes.

Significant Systemic Insulin Resistance is Associated With Unique Glioblastoma Multiforme Phenotype

Background

Some glioblastoma multiforme (GBM) are characterized by the presence of gemistocytes (GCs), a unique phenotype of reactive astrocytes. Certain GCs can be identified as neoplastic cells but these cells were also found to be associated with diabetes in non-neoplastic lesions of the central nervous system. Our aim was to find a correlation between insulin - resistance metabolic features and the presence of GCs in patients with newly diagnosed GBM.

Methods

Medical records from histologically confirmed GBM patients were retrospectively extracted for different systemic metabolic variables. A statistic-based comparison was made between GBM, diabetic patients with and without GC. Patients with poorly controlled diabetes (ie, hemoglobin A1C ⩾ 8.0) were also compared between the 2 groups.

Results

A total of 220 newly diagnosed GBM patients were included in our study. 58 (26.3%) patients had a history of diabetes mellitus type 2 (DM2) at the time of admission. The rate of poorly-controlled DM2 was nearly as twice in the GC-GBM group than in the non-GC GBM group (18.75% vs 9.5%; P = .130). In the DM2 cohort, the subgroup of GC-GBM was significantly associated with demographic and metabolic features related to insulin resistance such as male gender predominance (89% vs 50%, P = .073) and morbid obesity (weight ⩾85 kg: OR 6.16; P = .0019 and mean BMI: 34.1 ± 11.42 vs 28.7 ± 5.44; P = .034 for group with and without GCs, respectively). In the poorly-controlled DM2 group, none of the GC-GBM patients were using insulin prior to diagnosis, compared to 61.1% in the non-GC GBM patients (OR = 0.04, P = .045).

Conclusion

Systemic metabolic factors related to marked insulin resistance (DM2, morbid obesity, male gender) are associated with a unique histologic phenotype of GBM, characterized by the presence of GCs. This feature is prominent in poorly-controlled DM2 GBM patients who are not using synthetic insulin. This novel finding may add to the growing data on the relevance of glucose metabolism in astrocytes and in astrocytes associated with high-grade gliomas. In GBM patients, a correlation between patients' metabolic status, tumor's histologic phenotype, tumor's molecular changes, use of anti-diabetic drugs and the respective impact of these factor on survival warrants further investigation.

The risk of childhood brain tumors associated with delivery interventions: A Danish matched case-control study

BACKGROUND

Head trauma has been associated with increased brain tumor risk in adults. Instrument assisted delivery can be a cause of head trauma in newborns. The goal of this study was to determine if instrument-assisted deliveries influenced the odds of childhood brain tumors in Denmark.

METHODS

We conducted a matched case-control study of childhood (<20 years) brain tumors in Denmark born between 1978 and 2013 and diagnosed 1978-2016. A total of 1678 brain tumor cases were identified and 25 controls were matched to each case based on the child's sex and birth date (N = 40,934). Conditional logistic regression was used to estimate effects (odds ratios (OR) and 95% confidence intervals (95%CI)) for variables of interest.

RESULTS

Compared to children birthed by spontaneous vaginal delivery, children who later developed ependymomas (N = 118) had a greater likelihood of having experienced vacuum assisted deliveries (OR=1.74, 95% CI 1.02-2.96). Forceps use was low, and declined across the study period. We did not observe an overall increase in all CNS tumors (combined) with either vacuum delivery (OR=0.99, 95% CI 0.84-1.18) or forceps delivery (OR=1.26, 95% CI 0.78-2.03).

CONCLUSION

Our findings suggest an association between vacuum assisted deliveries and ependymomas.

Searching for causal relationships of glioma: a phenome-wide Mendelian randomisation study

BACKGROUND

The aetiology of glioma is poorly understood. Summary data from genome-wide association studies (GWAS) can be used in a Mendelian randomisation (MR) phenome-wide association study (PheWAS) to search for glioma risk factors.

METHODS

We performed an MR-PheWAS analysing 316 phenotypes, proxied by 8387 genetic variants, and summary genetic data from a GWAS of 12,488 glioma cases and 18,169 controls. Causal effects were estimated under a random-effects inverse-variance-weighted (IVW-RE) model, with robust adjusted profile score (MR-RAPS), weighted median and mode-based estimates computed to assess the robustness of findings. Odds ratios per one standard deviation increase in each phenotype were calculated for all glioma, glioblastoma (GBM) and non-GBM tumours.

RESULTS

No significant associations (P < 1.58 × 10-4) were observed between phenotypes and glioma under the IVW-RE model. Suggestive associations (1.58 × 10-4 < P < 0.05) were observed between leukocyte telomere length (LTL) with all glioma (ORSD = 3.91, P = 9.24 × 10-3) and GBM (ORSD = 4.86, P = 3.23 × 10-2), but the association was primarily driven by the TERT variant rs2736100. Serum low-density lipoprotein cholesterol and plasma HbA1C showed suggestive associations with glioma (ORSD = 1.11, P = 1.39 × 10-2 and ORSD = 1.28, P = 1.73 × 10-2, respectively), both associations being reliant on single genetic variants.

CONCLUSIONS

Our study provides further insight into the aetiological basis of glioma for which published data have been mixed.

The effects of chitosan-based materials on glioma: Recent advances in its applications for diagnosis and treatment

Glioma is known as the most common primary brain tumor occurring in adolescents and is considered as a lethal disease worldwide. Despite the advancements in presently available therapeutic approaches (i.e. radiation therapy and chemotherapy), the rate of amelioration in glioma patients is still low. In this regard, it seems that there is a need for reconsidering and enhancing current therapies and/or discovering novel therapeutic platforms. Chitosan is a natural polysaccharide with several beneficial characteristics, including biocompatibility, biodegradability, and low toxicity. Without causing toxic effects on healthy cells, chitosan nanoparticles are attractive targets in cancer therapy which lead to the sustained release and enhanced internalization of chemotherapeutic drugs as well as higher cytotoxicity for cancer cells. Hence, these properties turn it into a suitable candidate for the treatment of various cancers, including glioma. In the viewpoint of glioma, cancer inhibition is possible through targeting glioma-associated signaling pathways and molecules such as MMP-9, VEGF, TRAIL and nuclear factor-κB by chitosan and its derivatives. Moreover, it has been acknowledged that chitosan and its derivatives can be applied as a delivery system for carrying a diverse range of therapeutic agents to the tumor site. Besides the anti-glioma effects of chitosan and its derivatives, these molecules can be utilized for culturing glioma cancer cells; providing a better understanding of glioma pathogenesis. Furthermore, it is documented that 3D chitosan scaffolds are potential targets that offer advantageous drug screening platforms. Herein, we summarized the anti-glioma effects of chitosan and also its utilization as drug delivery systems in the treatment of glioma.

Local and Systemic Immune Dysregulation Alters Glioma Growth in Hyperglycemic Mice

PURPOSE

Unlike most cancers, no clear epidemiological correlation between diabetes (Db) and malignant glioma progression exists. Because hyperglycemia activates proinflammatory pathways through the receptor for advanced glycation endproducts (RAGE), we hypothesized that Db can also promote malignant glioma progression.

EXPERIMENTAL DESIGN

We compared the growth of two phenotypically diverse syngeneic glioma models in control and diabetic mice. Tumor growth and antitumor immune responses were evaluated in orthotopic and heterotopic models and correlated to RAGE and RAGE ligand expression.

RESULTS

Irrespective of tumor implantation site, growth of a "classical" glioma model, GL261, increased in hyperglycemic mice and was mediated by upregulation of RAGE and its ligand, HMGB1. However, growth of a "mesenchymal" glioma subtype, K-Luc, depended on tumor implantation site. Whereas heterotopic K-Luc tumors progressed rapidly in Db mice, intracranial K-Luc tumors grew slower. We further showed that hyperglycemia inhibited the innate antitumor inflammatory responses in both models. Although this contributed to the accelerated growth of heterotopic tumors, suppression of tumor inflammatory responses dampened the growth of orthotopic K-Luc gliomas.

CONCLUSIONS

Hyperglycemia may enhance glioma growth through promotion of RAGE expression and suppression of antitumor immune responses. However, abrogation of the proinflammatory milieu in tumors may also dampen the growth of inflammatory glioma subtypes in the brains of diabetic mice. This dichotomy in glioma growth response to hyperglycemia may partly explain why conflicting epidemiological studies show both an increased risk and a protective effect of Db in patients with malignant gliomas.

Autoimmune diseases and immunosuppressive therapy in relation to the risk of glioma

Effectors from the immune system can modulate the course and possibly the early development of gliomas. We, therefore, hypothesized that autoimmune diseases associated with increased immune‐surveillance may also modulate the risk of human glioma. To test this hypothesis, we used data from the well‐validated Clinical Practice Research Datalink (CPRD) GOLD from the UK to analyze the association of immune‐related disorders or use of immunosuppressive drugs and the risk of glioma. We identified 3112 incident glioma cases diagnosed between 1995 and 2017. We randomly selected up to 10 controls, matching them to glioma cases on age, sex, index date, general practice, and number of years of active history in the database prior to the index date. We performed conditional logistic regression analyses to estimate Odds Ratios (ORs) of glioma among those exposed to allergies, autoimmune diseases, and immunosuppressive drugs. Overall, we found no materially altered association between a history of any autoimmune disease (OR 0.98, 95% CI 0.86‐1.11), allergy (OR 0.97, 95% CI 0.89‐1.05), or use of immunosuppressive drugs and the risk of glioma. However, subgroup analyses among younger patients found a statistically significant increased risk of glioma in patients with a history of inflammatory bowel disease (IBD) (OR 2.59, 95% CI 1.31‐5.12). There was also an inverse association between asthma and risk of glioma in patients with longer survival (OR 0.73, 95% CI 0.58‐0.91) and between long‐term duration diabetes and risk of glioma (OR 0.71, 95% CI 0.53‐0.96).

Maternal diabetes and risk of childhood cancer in the offspring

An association between maternal diabetes, its medication and childhood cancer has not been previously explored in a registry-based setting. With a case-control design, we aimed to explore whether maternal diabetes is associated with an increased risk of childhood cancer in the offspring. Combining data from population-based registries, we analyzed a total of 2,029 cases, that is, persons with childhood cancer diagnosed under the age of 20 years between years 1996-2014 and a total of 10,103 matched population controls. The mothers of the cases/controls and their diagnoses of diabetes (DM) before/during pregnancy as well as their insulin/metformin prescriptions during pregnancy were identified. Conditional logistic regression modeling was used to analyze the risk of childhood cancer. The OR for childhood cancer among those exposed to any maternal diabetes was 1.32 (95% CI 1.14-1.54) compared to the offspring of the nondiabetic mothers. The effect of maternal diabetes on the risk of childhood cancer remained elevated even after adjusting for maternal age, parity and smoking. Our data suggest that maternal diabetes medication may reduce the risk for childhood cancer (adjusted OR 0.83, 95% CI 0.36-1.94), especially in gestational diabetes (adjusted OR 0.26, 95% CI 0.05-1.25), compared to the diabetic mothers without medication. The risk of childhood leukemia was significantly higher among children exposed to any maternal diabetes (OR 1.36, CI 1.04-1.77) compared to the unexposed. Maternal diabetes appears to be associated with an increased risk of childhood cancer in the offspring. The possible risk-reducing effect of an exposure to diabetes medication on offspring cancer risk warrants further investigation.

Genetic Variants Related to Cell Cycle and Stability of Telomere in Patients with Glioma

Background:

Glioma, most common primary malignant brain tumor in adults, is highly aggressive and associated with a poor prognosis. Evaluate the association of polymorphisms related of to the cell cycle, integrity and DNA repair with gliomas, as well as lifestyle habits, comorbidities, survival and response to treatment.

Methods:

Were studied 303 individuals distributed into: Study Group - 100 patients with gliomas, regardless of the degree of malignancy, and Control Group - 203 individuals without clinical signs of the disease. These polymorphisms were genotyped by TaqMan^® SNP Genotyping Assay. Significance level was set at 5%.

Results:

Smoking, alcohol consumption, systemic arterial hypertension (SAH) and diabetes mellitus (DM) prevailed in patients, compared to controls (P=0.0088, P=0.0001, P=0.0001, P=0.0011, respectively). In the logistic regression analysis, alcohol consumption and SAH were identified as independent risk factors for gliomas (P=0.0001, P=0.0027, respectively). Patients with low-grade gliomas showed survival in one year (92.0±6.8%), compared to patients with high-grade gliomas (24.0±5.3; P=0.011).

Conclusion:

Polymorphisms involved in cell cycle, telomere protection and stability and DNA repair are not associated with gliomas. On the other hand, alcohol consumption and SAH stand out as independent risk factors for the disease. Low-grade gliomas, response to treatment and the combination of chemotherapy with Temozolomide and radiation therapy show increased survival of patients.

Does diabetes decrease the risk of glioma? A systematic review and meta-analysis of observational studies

PURPOSE

Increasing epidemiologic evidence suggests that diabetes mellitus (DM) may be associated with a decreased risk of glioma. This systematic review assessed whether DM was associated with glioma risk.

METHODS

Electronic searches were performed in PubMed, Web of Science, EMBASE, and Cochrane Library databases up to August 30, 2018. A random-effects model was performed to calculate summary effect size with corresponding 95% confidence intervals (CIs).

RESULTS

In total, 10 studies (eight case-control studies and two cohort studies) matched the inclusion criteria. Meta-analyses of case-control studies showed that DM decreased the risk of glioma by 23% (odds ratio: 0.77, 95% CI: 0.61-0.96; P = .02, I2 = 82.0%). However, no such effect was observed in cohort studies (relative risk: 0.71, 95% CI: 0.10-4.80; P = .72, I2 = 61.6%). In the subgroup analyses, DM was associated with a decreased risk of glioma in Caucasians but not in Asians; the inverse association was slightly higher in males than in females.

CONCLUSIONS

Our results indicate that DM decreases the risk of glioma, but the inverse association may vary in subgroups. The present conclusions should be confirmed with further studies.

Use of Mendelian andomization for dentifying isk actors for rain umors

Gliomas are a group of primary brain tumors, the most common and aggressive subtype of which is glioblastoma. Glioblastoma has a median survival of just 15 months after diagnosis. Only previous exposure to ionizing radiation and particular inherited genetic syndromes are accepted risk factors for glioma; the vast majority of cases are thought to occur spontaneously. Previous observational studies have described associations between several risk factors and glioma, but studies are often conflicting and whether these associations reflect true casual relationships is unclear because observational studies may be susceptible to confounding, measurement error and reverse causation. Mendelian randomization (MR) is a form of instrumental variable analysis that can be used to provide supporting evidence for causal relationships between exposures (e.g., risk factors) and outcomes (e.g., disease onset). MR utilizes genetic variants, such as single nucleotide polymorphisms (SNPs), that are robustly associated with an exposure to determine whether there is a causal effect of the exposure on the outcome. MR is less susceptible to confounding, reverse causation and measurement errors as it is based on the random inheritance during conception of genetic variants that can be relatively accurately measured. In previous studies, MR has implicated a genetically predicted increase in telomere length with an increased risk of glioma, and found little evidence that obesity related factors, vitamin D or atopy are causal in glioma risk. In this review, we describe MR and its potential use to discover and validate novel risk factors, mechanistic factors, and therapeutic targets in glioma.

Influence of obesity-related risk factors in the aetiology of glioma

BACKGROUND

Obesity and related factors have been implicated as possible aetiological factors for the development of glioma in epidemiological observation studies. We used genetic markers in a Mendelian randomisation framework to examine whether obesity-related traits influence glioma risk. This methodology reduces bias from confounding and is not affected by reverse causation.

METHODS

Genetic instruments were identified for 10 key obesity-related risk factors, and their association with glioma risk was evaluated using data from a genome-wide association study of 12,488 glioma patients and 18,169 controls. The estimated odds ratio of glioma associated with each of the genetically defined obesity-related traits was used to infer evidence for a causal relationship.

RESULTS

No convincing association with glioma risk was seen for genetic instruments for body mass index, waist-to-hip ratio, lipids, type-2 diabetes, hyperglycaemia or insulin resistance. Similarly, we found no evidence to support a relationship between obesity-related traits with subtypes of glioma-glioblastoma (GBM) or non-GBM tumours.

CONCLUSIONS

This study provides no evidence to implicate obesity-related factors as causes of glioma.

Genome-Wide Association Studies in Glioma

Since the first reports in 2009, genome-wide association studies (GWAS) have been successful in identifying germline variants associated with glioma susceptibility. In this review, we describe a chronological history of glioma GWAS, culminating in the most recent study comprising 12,496 cases and 18,190 controls. We additionally summarize associations at the 27 glioma-risk SNPs that have been reported so far. Future efforts are likely to be principally focused on assessing association of germline-risk SNPs with particular molecular subgroups of glioma, as well as investigating the functional basis of the risk loci in tumor formation. These ongoing studies will be important to maximize the impact of research into glioma susceptibility, both in terms of insight into tumor etiology as well as opportunities for clinical translation. Cancer Epidemiol Biomarkers Prev; 27(4); 418-28. ©2018 AACRSee all articles in this CEBP Focus section, "Genome-Wide Association Studies in Cancer."

Prognostication of Survival Outcomes in Patients Diagnosed with Glioblastoma

OBJECTIVE

Glioblastoma multiforme (GBM) is an aggressive primary brain tumor with dismal survival. This study aims to examine the prognostic value of primary tumor sites and race on survival outcomes.

METHODS

Patient data obtained from the Scott and White Hospital Brain Tumor Registry (1976-2013) were stratified according to sex, age, race, primary tumor site, vital status, and survival.

RESULTS

Of the 645 patients, 580 (89.9%) were diagnosed with GBM not otherwise specified (GBM NOS), 57 (8.8%) with GBM, and 8 (1.2%) with giant-cell GBM. Most were male (53.5%), aged 50 years or older (78.7%). The white population had the highest GBM prevalence (87.1%) and the lowest overall survival versus all other race groups (6.6% vs. 30.1%; P < 0.01). The black population had a relatively low prevalence of GBM (5.9%) and the greatest overall survival versus all others (47.4% vs. 7.3%; P < 0.01). Primary tumor sites located in the temporal (25.8% vs. 20.2%; P = 0.03), occipital (8.1% vs. 2.9%; P = 0.05), and parietal lobes (24.2% vs. 20.8%; P = 0.05) had a greater occurrence in surviving individuals. The overall survival for men versus women was (62.9% vs. 37.1%; P = 0.12).

CONCLUSIONS

Black racial background and temporal, occipital, or parietal primary tumor sites are suggestive of positive survival outcomes. Conversely, white racial background with primary tumor sites in the brain overlapping and NOS areas seem to be associated with negative outcomes and decreased survival. Thus, racial background and primary tumor site may be useful prognostic factors in patients with GBM.

Maternal diabetes and incidence of childhood cancer - a nationwide cohort study and exploratory genetic analysis

Background

The etiology of childhood cancer is not well understood, but may be linked to prenatal and perinatal factors, such as maternal diabetes. However, this association has not been examined in depth. We aimed to determine if maternal diabetes is associated with risk of childhood brain tumor (CBT), leukemia (all types combined and acute lymphoblastic leukemia [ALL] separately), and lymphoma.

Methods

All children born in Sweden between 1973 and 2014 (n=4,239,965) were followed from birth until first cancer diagnosis, age 15 years, or December 31, 2015. Data on maternal diabetes, childhood cancer, and covariates were obtained from nationwide health registers. Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated using Cox regression adjusted for potential confounders/mediators. Additionally, we performed an exploratory analysis using results from published genome-wide association studies and functional annotation.

Results

Maternal diabetes was associated with lower risk of CBT (adjusted IRR [95% CI]: 0.56 [0.35-0.91]) and higher risk of leukemia (adjusted IRR: 1.47 [1.13-1.92] for all leukemia combined and 1.64 [1.23-2.18] for ALL). These associations were similar for both maternal type 1 diabetes and gestational diabetes. Associations of five previously identified genetic loci were compatible with a causal effect of diabetes traits on neuroblastoma and common Hodgkin's lymphoma.

Conclusion

Children whose mother had diabetes had lower risk of CBT and higher risk of leukemia, compared with children whose mother did not have diabetes. Our results are compatible with a role of prenatal and perinatal glycemic environment in childhood cancer etiology.

Type 2 Diabetes Mellitus and Glioblastoma Multiforme-Assessing Risk and Survival: Results of a Large Retrospective Study and Systematic Review of the Literature

OBJECTIVE

Despite studies showing a positive correlation between type 2 diabetes mellitus (DM2), a modifiable risk factor, and various cancer types, the link remains controversial in the setting of glioblastoma multiforme (GBM). In this study, we assessed whether DM2 and DM2-associated factors were associated with a higher risk of developing GBM and also determined if DM2 affected the survival of patients with GBM.

METHODS

A cross-sectional case-control study of 1144 GBM cases diagnosed between 2000 and 2013 of which 969 patients matched for age and sex was performed to assess the association between DM2, hyperlipidemia, and obesity with the incidence of GBM. A longitudinal study of the patients with GBM was also performed to assess the association between the effect of DM2 and GBM survival.

RESULTS

No association was seen between DM2, hyperlipidemia, obesity, and GBM. DM2 was associated with poorer survival in univariate testing yet not in multivariate testing. Diabetic patients with GBM had good glycemic control. Older patients had poorer survival and overall survival improved over years of study.

CONCLUSIONS

DM2, hyperlipidemia, and obesity were not associated with increased risk of developing GBM, and DM2 itself does not seem to influence survival among these patients. This finding might be related to good glycemic control in this cohort. Survey of the literature consistently shows that hyperglycemia is associated with poorer survival. Our findings suggest that rather than the presence or absence of DM2, glycemic control seems to be more important in the survival of patients with GBM, which warrants future investigation.

Neurological outcomes of antidiabetic therapy: What the neurologist should know

Considering the causative or contributory effects of diabetes mellitus on common neurological diseases such as polyneuropathy, stroke and dementia, modern antidiabetic drugs may be expected to reduce incidence or progression of these conditions. Nevertheless, most observed benefits have been small, except in the context of therapy for diabetes mellitus type I and new-onset polyneuropathy. Recently, semaglutide, a GLP-1 analog, has been shown to significantly reduce stroke incidence in a randomized controlled trial. Beneficial effects of antidiabetic drugs on stroke severity or outcome have been controversial, though. The level of risk conferred by diabetes mellitus, the complex pathophysiology of neurological diseases, issues of trial design, side-effects of antidiabetic drugs as well as co-medication might be interacting factors that determine the performance of antidiabetic therapy with respect to neurological outcomes. It might be speculated that early treatment of prediabetes might prevent cerebral arteriosclerosis, cognitive decline or polyneuropathy more effectively, but this remains to be demonstrated.

Associations between prediagnostic blood glucose levels, diabetes, and glioma

Previous literature indicates that pre-diagnostic diabetes and blood glucose levels are inversely related to glioma risk. To replicate these findings and determine whether they could be attributed to excess glucose consumption by the preclinical tumour, we used data from the Apolipoprotein MOrtality RISk (AMORIS) (n = 528,580) and the Metabolic syndrome and Cancer project (Me-Can) cohorts (n = 269,365). We identified individuals who were followed for a maximum of 15 years after their first blood glucose test until glioma diagnosis, death, emigration or the end of follow-up. Hazard ratios (HRs), 95% confidence intervals (CIs) and their interactions with time were estimated using Cox time-dependent regression. As expected, pre-diagnostic blood glucose levels were inversely related to glioma risk (AMORIS, P_trend = 0.002; Me-Can, P_trend = 0.04) and pre-diagnostic diabetes (AMORIS, HR = 0.30, 95% CI 0.17 to 0.53). During the year before diagnosis, blood glucose was inversely associated with glioma in the AMORIS (HR = 0.78, 95% CI 0.66 to 0.93) but not the Me-Can cohort (HR = 0.99, 95% CI 0.63 to 1.56). This AMORIS result is consistent with our hypothesis that excess glucose consumption by the preclinical tumour accounts for the inverse association between blood glucose and glioma. We discuss additional hypothetical mechanisms that may explain our paradoxical findings.

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

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

Relation between Established Glioma Risk Variants and DNA Methylation in the Tumor

Genome-wide association studies and candidate gene studies have identified several genetic variants that increase glioma risk. The majority of these variants are non-coding and the mechanisms behind the increased risk in carriers are not known. In this study, we hypothesize that some of the established glioma risk variants induce aberrant DNA methylation in the developing tumor, either locally (gene-specific) or globally (genome-wide). In a pilot data set including 77 glioma patients, we used Illumina beadchip technology to analyze genetic variants in blood and DNA methylation in matched tumor samples. To validate our findings, we used data from the Cancer Genome Atlas, including 401 glioblastoma patients. Consensus clustering identified the glioma CpG island methylator phenotype (gCIMP) and two additional subgroups with distinct patterns of global DNA methylation. In the pilot dataset, gCIMP was associated with two genetic variants in CDKN2B-AS1, rs1412829 and rs4977756 (9p21.3, p = 8.1 x 10-7 and 4.8 x 10-5, respectively). The association was in the same direction in the TCGA dataset, although statistically significant only when combining individuals with AG and GG genotypes. We also investigated the relation between glioma risk variants and DNA methylation in the promoter region of genes located within 30 kb of each variant. One association in the pilot dataset, between the TERT risk variant rs2736100 and lower methylation of cg23827991 (in TERT; p = 0.001), was confirmed in the TCGA dataset (p = 0.001). In conclusion, we found an association between rs1412829 and rs4977756 (9p21.3, CDKN2B-AS1) and global DNA methylation pattern in glioma, for which a trend was seen also in the TCGA glioblastoma dataset. We also found an association between rs2736100 (in TERT) and levels of methylation at cg23827991 (localized in the same gene, 3.3 kbp downstream of the risk variant), which was validated in the TCGA dataset. Except for this one association, we did not find strong evidence for gene-specific DNA methylation mediated by glioma risk variants.

Coffee and green tea consumption in relation to brain tumor risk in a Japanese population

Few prospective studies have investigated the etiology of brain tumor, especially among Asian populations. Both coffee and green tea are popular beverages, but their relation with brain tumor risk, particularly with glioma, has been inconsistent in epidemiological studies. In this study, we evaluated the association between coffee and greed tea intake and brain tumor risk in a Japanese population. We evaluated a cohort of 106,324 subjects (50,438 men and 55,886 women) in the Japan Public Health Center-Based Prospective Study (JPHC Study). Subjects were followed from 1990 for Cohort I and 1993 for Cohort II until December 31, 2012. One hundred and fifty-seven (70 men and 87 women) newly diagnosed cases of brain tumor were identified during the study period. Hazard ratio (HR) and 95% confidence intervals (95%CIs) for the association between coffee or green tea consumption and brain tumor risk were assessed using a Cox proportional hazards regression model. We found a significant inverse association between coffee consumption and brain tumor risk in both total subjects (≥3 cups/day; HR = 0.47, 95%CI = 0.22-0.98) and in women (≥3 cups/day; HR = 0.24, 95%CI = 0.06-0.99), although the number of cases in the highest category was small. Furthermore, glioma risk tended to decrease with higher coffee consumption (≥3 cups/day; HR = 0.54, 95%CI = 0.16-1.80). No association was seen between green tea and brain tumor risk. In conclusion, our study suggested that coffee consumption might reduce the risk of brain tumor, including that of glioma, in the Japanese population.

Insulin-mediated signaling promotes proliferation and survival of glioblastoma through Akt activation

BACKGROUND

Metabolic complications such as obesity, hyperglycemia, and type 2 diabetes are associated with poor outcomes in patients with glioblastoma. To control peritumoral edema, use of chronic high-dose steroids in glioblastoma patients is common, which can result in de novo diabetic symptoms. These metabolic complications may affect tumors via profound mechanisms, including activation of insulin receptor (InsR) and the related insulin-like growth factor 1 receptor (IGF1R) in malignant cells.

METHODS

In the present study, we assessed expression of InsR in glioblastoma surgical specimens and glioblastoma response to insulin at physiologically relevant concentrations. We further determined whether genetic or pharmacological targeting of InsR affected oncogenic functions of glioblastoma in vitro and in vivo.

RESULTS

We showed that InsR was commonly expressed in glioblastoma surgical specimens and xenograft tumor lines, with mitogenic isoform-A predominating. Insulin at physiologically relevant concentrations promoted glioblastoma cell growth and survival, potentially via Akt activation. Depletion of InsR impaired cellular functions and repressed orthotopic tumor growth. The absence of InsR compromised downstream Akt activity, but yet stimulated IGF1R expression. Targeting both InsR and IGF1R with dual kinase inhibitors resulted in effective blockade of downstream signaling, loss of cell viability, and repression of xenograft tumor growth.

CONCLUSIONS

Taken together, our work suggests that glioblastoma is sensitive to the mitogenic functions of insulin, thus significant insulin exposure imposes risks to glioblastoma patients. Additionally, dual inhibition of InsR and IGF1R exhibits promise for treating glioblastoma.

Diabetes, use of antidiabetic drugs, and the risk of glioma

BACKGROUND

Prior epidemiologic studies suggest inverse relations between diabetes and glioma risk, but the underlying mechanisms, including use of antidiabetic drugs, are unknown.

METHODS

We therefore performed a matched case-control analysis using the Clinical Practice Research Datalink (CPRD). We identified incident glioma cases diagnosed between 1995 and 2012 and matched each case with 10 controls on age, gender, calendar time, general practice, and years of active history in the CPRD. We performed conditional logistic regression to estimate odds ratios (ORs) with 95% CIs, adjusted for body mass index and smoking.

RESULTS

We identified 2005 cases and 20 050 controls. Diabetes was associated with decreased risk of glioma (OR = 0.74; 95% CI = 0.60-0.93), particularly glioblastoma (OR = 0.69; 95% CI = 0.51-0.94). Glioblastoma risk reduction was markedly pronounced among diabetic men (OR = 0.60; 95% CI = 0.40-0.90), most apparently for those with diabetes of long-term duration (OR for >5 vs 0 y = 0.46; 95% CI = 0.26-0.82) or poor glycemic control (OR for HbA1c ≥ 8 vs <6.5% = 0.20; 95% CI = 0.06-0.70). In contrast, the effect of diabetes on glioblastoma risk was absent among women (OR = 0.85; 95% CI = 0.53-1.36). No significant associations with glioma were found for use of metformin (OR for ≥ 30 vs 0 prescriptions = 0.72; 95% CI = 0.38-1.39), sulfonylureas (OR = 0.71; 95% CI = 0.39-1.30), or insulin (OR = 0.79; 95% CI = 0.37-1.69).

CONCLUSIONS

Antidiabetic treatment appears to be unrelated to glioma, but long-term diabetes duration and increased HbA1c both show decreased glioma risk. Stronger findings in men than women suggest low androgen levels concurrent with diabetes as a biologic mechanism.

Trends in incidence of primary brain cancer in New Zealand, 1995 to 2010

OBJECTIVE

Case-control studies have linked mobile phone use to an increased risk of glioma in the most exposed brain areas, the temporal and parietal lobes, although inconsistently. We examined time trends in the incidence rates of brain malignancies in New Zealand from 1995 to 2010.

METHODS

Data from the New Zealand Cancer Registry was used to calculate incidence rates of primary brain cancer, by age, gender, morphology and anatomical site. Log-linear regression analysis was used to assess trends in the annual incidence of primary brain cancer; annual percentage changes and their 95% confidence intervals were estimated.

RESULTS

No consistent increases in all primary brain cancer, glioma, or temporal or parietal lobe glioma were seen. At ages 10-69, the incidence of all brain cancers declined significantly. Incidence of glioma increased at ages over 70.

CONCLUSION

In New Zealand, there has been no consistent increase in incidence rates of primary brain cancers. An increase in glioma at ages over 70 is likely to be due to improvements in diagnosis. As with any such studies, a small effect, or one with a latent period of more than 10 to 15 years, cannot be excluded.

Statin use and survival following glioblastoma multiforme

AIM

While some studies indicate a potential chemopreventive effect of statin use on the risk of glioma, the effect of statins on the prognosis of brain tumours has not yet been examined. We thus conducted a cohort study evaluating the influence of statin use on survival in patients with glioblastoma multiforme (GBM).

METHODS

We identified 1562 patients diagnosed with GBM during 2000-2009 from the Danish Cancer Registry and linked this cohort to Danish nationwide demographic and health registries. Within the GBM cohort, each patient recorded as using statins prior to diagnosis (defined as ≥ 2 redeemed prescriptions) was matched to two statin non-users (<2 redeemed prescriptions) by propensity scores based on age, gender, year of diagnosis, comorbidity, and use of selected drugs. Cox proportional hazard models were used to compute hazard ratios (HRs) and 95% confidence intervals (CI) for all-cause death associated with prediagnostic statin use.

RESULTS

A total of 339 GBM patients were included in the analyses. Of these, 325 died during median follow-up of 6.9 months (interquartile range: 3.8-13.4 months). Prediagnostic statin use was associated with a reduced HR of death (0.79; 95% CI: 0.63-1.00). The HRs decreased with increasing duration or intensity of prediagnostic statin use [long-term (≥ 5 years) statin use: HR 0.75 (95% CI: 0.47-1.20); high-intensity statin use: HR 0.66 (95% CI: 0.44-0.98)]. Additional adjustment for oncotherapeutic modalities yielded similar results (overall HR 0.80, 95% CI: 0.63-1.01).

CONCLUSION

Long-term prediagnostic statin use may improve survival following GBM.

Adult brain cancer in the U.S. black population: a Surveillance, Epidemiology, and End Results (SEER) analysis of incidence, survival, and trends

Background

Despite much epidemiological research on brain cancer in the United States, the etiology for the various subtypes remains elusive. The black population in the United States currently experiences lower incidence but higher survival rates when compared to other races. Thus, the aim of this study is to analyze the trends in incidence and survival for the 6 most common primary brain tumors in the black population of the United States.

Material/Methods

The Surveillance, Epidemiology, and End Results (SEER) database was utilized in this study to analyze the incidence and survival rates for the 6 most common brain tumor subtypes. Joinpoint 3.5.2 software was used to analyze trends in the incidence of diagnosis from 1973 to 2008. A Kaplan-Meier curve was generated to analyze mean time to death and survival at 60 months.

Results

Joinpoint analysis revealed that per year the incidence of brain cancer in the U.S. black population increased by 0.11 between 1973 and 1989. After this period, a moderate decrease by 0.06 per annum was observed from 1989 to 2008. Lymphoma was the most common primary tumor subtype for black individuals ages 20–34, and glioblastoma was identified as the most common tumor subtype for black individuals in the age groups of 35–49, 50–64, 65–79, and 80+.

Conclusions

This population-based retrospective study of brain cancer in black adults in the United States revealed significant sex and age differences in the incidence of the 6 most common brain tumor subtypes from 1973 to 2008.

Immune-related conditions and subsequent risk of brain cancer in a cohort of 4.5 million male US veterans

Background:

Case–control studies have reported an inverse association between self-reported history of allergy and risk of glioma, but cohort data are limited. Our objectives were to evaluate the associations of major groups of medically diagnosed immune-related conditions (allergy/atopy, autoimmune disease, diabetes, infectious/inflammatory disease) and to explore associations with specific conditions in relation to subsequent diagnosis of brain cancer in a large cohort study.

Methods:

We used hospital discharge records for a cohort of 4.5 million male US veterans, of whom 4383 developed primary brain cancer. Rate ratios (RRs) and 95% confidence intervals (CIs) were calculated using time-dependent Poisson regression.

Results:

We found a significant trend of decreasing RRs for brain cancer with longer duration of allergy/atopy (P=0.02), but not for other conditions studied. Rate ratios of brain cancer for allergy/atopy and diabetes with duration of 10 or more years were 0.60 (95% CI: 0.43, 0.83) and 0.75 (95% CI: 0.62, 0.93), respectively. Several associations with specific conditions were found, but these did not withstand correction for multiple comparisons.

Conclusions:

This study lends some support to an inverse association between allergy/atopy and diabetes of long duration and brain cancer risk, but prospective studies with biological samples are needed to uncover the underlying biological mechanisms.