Comorbidity indices in observational studies on cancer risk

Previous observational studies have focused on the link between type 2 diabetes and the risk of cancer. However, the association between type 1 diabetes and the risk of cancer has not been well addressed. This study aimed to investigate the association between type 1 diabetes and the risk of cancer by using a meta-analysis of observational studies. We searched PubMed and EMBASE for observational studies that examined the association between type 1 diabetes and cancer in April 2017. We calculated the pooled odds ratios (ORs) or relative risks (RRs) with confidence intervals (CIs) from individual studies based on a random-effects model meta-analysis. We included a total of 15 observational studies with two case-control studies and 13 cohort studies involving 31 893 cancer patients among a total of 1 915 179 participants in the final analysis. In the random-effects meta-analysis of all studies, patients with type 1 diabetes had an increased risk of cancer (OR or RR, 1.29; 95% CI, 1.09-1.52; n = 15; I2 = 95.2%). In the subgroup meta-analysis by type of cancer, type 1 diabetes significantly increased the risk of cancers of stomach, lung, pancreas, liver, ovary and kidney, whereas it significantly decreased the risk of breast cancer (OR or RR, 0.91; 95% CI, 0.86-0.95; n = 9; I2 = 0%). This meta-analysis suggests that type 1 diabetes is associated with the increased risk of several types of cancer and the decreased risk of breast cancer. However, the plausible mechanisms for the decreased risk of breast cancer remain unclear. Further prospective studies with proper adjustment for possible confounding factors are warranted.

Cholesterol and Cancer: Answers and New Questions

Metformin and Cancer in Type 2 Diabetes

Optimizing clinical outcomes resulting from glucose‐lowering therapies in type 2 diabetes: increased confidence about the <scp>DPP</scp>‐4 inhibitors and continued concerns regarding sulphonylureas and exogenous insulin

Selenium for preventing cancer.

High coffee consumption is associated with low risk of mortality and morbidity, but the causality remains unclear. This review aims to discuss findings from observational studies on coffee consumption in context of Mendelian randomization studies. The PubMed database was searched for all Mendelian randomization studies on coffee consumption and corresponding observational studies. High coffee consumption is associated with low risk of all-cause and cardiovascular mortality in observational studies (HRs of 0.85-0.90 vs. no/low consumers), with no support of causality in Mendelian randomization studies. Moderate/high consumption is associated with low risk of cardiometabolic diseases, including ischemic heart disease (HRs of 0.85-0.90 vs. no/low consumption), stroke (HRs of approximately 0.80 vs. no/low consumption), type 2 diabetes (HRs of approximately 0.70 vs. no/low consumption) and obesity in observational studies, but not in Mendelian randomization studies. High consumption is associated with low risk of endometrial cancer and melanoma and high risk of lung cancer in observational studies, but with high risk of colorectal cancer in Mendelian randomization studies. In observational and Mendelian randomization studies, high coffee consumption is associated with low risk of gallstones (HRs of 0.55-0.70 for high vs. no/low self-reported and 0.81 (0.69-0.96) for highest vs. lowest genetic consumption). High coffee consumption is associated with low risk of mortality, cardiometabolic diseases, some cancers and gallstones in observational studies, with no evidence to support causality from Mendelian randomization studies for most diseases except gallstones.

Angiotensin-Converting Enzyme Inhibitors and Risk of Esophageal and Gastric Cancer: A Nested Case-Control Study

BackgroundThere is a scarcity of evidence on the carcinogenic risk associated with the use of ovulation induction agents (OIAs) for the treatment of infertility. We aimed to appraise the observational and interventional studies that describe the correlation between OIAs and the risk of developing various cancers in patients receiving infertility treatment.Materials and methodsPubMed/MEDLINE, SCOPUS, Embase, and Cochrane Library were searched from inception to December 2024. The observational studies that assessed the risk of cancers following the use of OIAs in patients with infertility were considered for this review. The studies included OIA combined with any other technique were excluded. Jonna Briggs Institute Checklist was employed to assess the methodological quality of the included studies. The synthesized evidence was narratively summarized as the data were highly heterogeneous.ResultsA total of 30 studies out of 4705 records from different parts of the world were included in this review. There was conflicting evidence on the risk of breast cancer, ovarian cancer, endometrial cancer, and uterine cancer. However, there was a significantly increased risk of non-Hodgkin lymphoma and thyroid cancer. In contrast to this, there is a significantly reduced risk of colorectal cancer associated with the use of OIA among infertile women.ConclusionThe current evidence suggests that there is no clear evidence of all types of cancer risk associated with OIA use among those with infertility. Further research is needed with a special emphasis on specific OIA and its time of administration in a diverse set of populations.Trial registrationPROSPERO CRD42023449708.

Epidemiological and retrospective clinical studies on cancer outcomes frequently adjust for patients' comorbid conditions. Despite the existence of multiple comorbidity indices, the Charlson comorbidity index (CCI) is the most frequently applied. Indices are developed in specific settings and the extent of alignment between the development setting and subsequent study is unclear. The present study provides a contemporaneous snapshot of comorbidity indices used in retrospective observational cancer studies and the extent to which cancer type(s), data source(s) and outcome(s) matched the studies in which the indices were developed. A systematic literature search in PubMed identified retrospective, observational studies on outcomes in patients with cancer published between March 2015 and March 2020. Information including the cancer type, data source and outcome were extracted and compared to those used in the validation study of the comorbidity index used. Of 158 papers reviewed, 79 used the CCI, either alone or in combination with other indices. The cancer type matched to that used in the validation study of the comorbidity index in 16 of the 115 studies using an established index, whilst the data source matched in 27 studies and outcome in only two. Justification was rarely provided for index choice (15 of the 115studies). It may be concluded that, while the CCI remains the dominant comorbidity index, it may not always align to key elements of the study design in terms of cancer type, data source and outcome. A range of indices exists and identification of the most appropriate measure has the potential to improve adjustment for comorbidity. The present study provided information about the indices used in included studies and encourages future studies to consider which comorbidity index offers the best alignment with the study population, data source and question addressed.

Frequency of adjustment with comorbidity and illness severity scores and indices in cardiac arrest research

American Gastroenterological Association Technical Review on the Diagnosis and Management of Lynch Syndrome

Background: Cannabis (also called marijuana or marihuana) is 1 of the most widely used illicit substances in the world. While cigarette smoking is a well-known risk factor of many cancers, effects of cannabis smoking on risk of developing cancer have remained unclear. Aim: This study is conducted to evaluate the association between cannabis smoking and cancer risk. Methods: We searched PubMed, Embase and the bibliographies of relevant articles to locate additional publications in October 2017. Two evaluators independently reviewed and selected eligible studies based on predetermined selection criteria. Observational studies such as cross-sectional, case-control, and cohort studies reporting odd ratios (ORs) or relative risk (RRs) for association between cannabis smoking and any kind of cancer risk were included. Subgroup analysis also was performed by cancer type (lung, oral, testicular, head and neck and others) and by smoking duration (&lt;5 years, 5-10 years, &gt;10 years). Results: We included 18 observational studies with 2 cohort studies and 16 case-controls studies, which involved a total of 13,646 cancer patients and 151,572 participants without cancer in final analysis. The random-effects meta-analysis of all 20 studies showed marginally statistically significant association between cannabis smoking and risk of lung cancer (OR = 1.76, 95% CI 1.00-3.08; I2 = 82.0%). Subgroup analysis by type of cancer shows that cannabis smoking more than 10 years increased risk of testicular cancer (OR = 1.50; 95% CI, 1.02-2.09; I2 = 00.0%). Conclusion: The current meta-analysis of observational studies found an overall significant increased risk of lung cancer and cannabis. Further, an increased risk of testicular cancer when duration of cannabis smoking exceeded 10 years also was found.

This review is an update of the first Cochrane publication on selenium for preventing cancer (Dennert 2011).Selenium is a metalloid with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancers. Two research questions were addressed in this review: What is the evidence for:1. an aetiological relation between selenium exposure and cancer risk in humans? and2. the efficacy of selenium supplementation for cancer prevention in humans? We conducted electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2013, Issue 1), MEDLINE (Ovid, 1966 to February 2013 week 1), EMBASE (1980 to 2013 week 6), CancerLit (February 2004) and CCMed (February 2011). As MEDLINE now includes the journals indexed in CancerLit, no further searches were conducted in this database after 2004. We included prospective observational studies (cohort studies including sub-cohort controlled studies and nested case-control studies) and randomised controlled trials (RCTs) with healthy adult participants (18 years of age and older). For observational studies, we conducted random effects meta-analyses when five or more studies were retrieved for a specific outcome. For RCTs, we performed random effects meta-analyses when two or more studies were available. The risk of bias in observational studies was assessed using forms adapted from the Newcastle-Ottawa Quality Assessment Scale for cohort and case-control studies; the criteria specified in the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the risk of bias in RCTs. We included 55 prospective observational studies (including more than 1,100,000 participants) and eight RCTs (with a total of 44,743 participants). For the observational studies, we found lower cancer incidence (summary odds ratio (OR) 0.69, 95% confidence interval (CI) 0.53 to 0.91, N = 8) and cancer mortality (OR 0.60, 95% CI 0.39 to 0.93, N = 6) associated with higher selenium exposure. Gender-specific subgroup analysis provided no clear evidence of different effects in men and women (P value 0.47), although cancer incidence was lower in men (OR 0.66, 95% CI 0.42 to 1.05, N = 6) than in women (OR 0.90, 95% CI 0.45 to 1.77, N = 2). The most pronounced decreases in risk of site-specific cancers were seen for stomach, bladder and prostate cancers. However, these findings have limitations due to study design, quality and heterogeneity that complicate interpretation of the summary statistics. Some studies suggested that genetic factors may modify the relation between selenium and cancer risk-a hypothesis that deserves further investigation.In RCTs, we found no clear evidence that selenium supplementation reduced the risk of any cancer (risk ratio (RR) 0.90, 95% CI 0.70 to 1.17, two studies, N = 4765) or cancer-related mortality (RR 0.81, 95% CI 0.49 to 1.32, two studies, N = 18,698), and this finding was confirmed when the analysis was restricted to studies with low risk of bias. The effect on prostate cancer was imprecise (RR 0.90, 95% CI 0.71 to 1.14, four studies, N = 19,110), and when the analysis was limited to trials with low risk of bias, the interventions showed no effect (RR 1.02, 95% CI 0.90 to 1.14, three studies, N = 18,183). The risk of non-melanoma skin cancer was increased (RR 1.44, 95% CI 0.95 to 1.17, three studies, N = 1900). Results of two trials-the Nutritional Prevention of Cancer Trial (NPCT) and the Selenium and Vitamin E Cancer Trial (SELECT)-also raised concerns about possible increased risk of type 2 diabetes, alopecia and dermatitis due to selenium supplements. An early hypothesis generated by NPCT that individuals with the lowest blood selenium levels at baseline could reduce their risk of cancer, particularly of prostate cancer, by increasing selenium intake has not been confirmed by subsequent trials. As the RCT participants were overwhelmingly male (94%), gender differences could not be systematically assessed. Although an inverse association between selenium exposure and the risk of some types of cancer was found in some observational studies, this cannot be taken as evidence of a causal relation, and these results should be interpreted with caution. These studies have many limitations, including issues with assessment of exposure to selenium and to its various chemical forms, heterogeneity, confounding and other biases. Conflicting results including inverse, null and direct associations have been reported for some cancer types.RCTs assessing the effects of selenium supplementation on cancer risk have yielded inconsistent results, although the most recent studies, characterised by a low risk of bias, found no beneficial effect on cancer risk, more specifically on risk of prostate cancer, as well as little evidence of any influence of baseline selenium status. Rather, some trials suggest harmful effects of selenium exposure. To date, no convincing evidence suggests that selenium supplements can prevent cancer in humans.

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Mushroom Consumption Is Associated with Low Risk of Cancer: A Systematic Review and Meta-Analysis of Observation Studies