Gamma-glutamyltransferase and cancer incidence: the Ohsaki cohort study

Circulating gamma-glutamyl transpeptidase and risk of pancreatic cancer: A prospective cohort study in the UK Biobank

BACKGROUND

To determine whether serum gamma-glutamyl transpeptidase (GGT) level is associated with pancreatic cancer risk in a large prospective cohort.

METHODS

The study analyzed serum GGT concentration at baseline of 421,032 participants recruited in the UK Biobank since 2006 through 2010. Information on incidence of pancreatic cancer was obtained from cancer and death registers, updated until 2015 in Scotland or 2016 in England and Wales. Adjusted Cox proportional hazards models were used to measure the association between serum GGT and pancreatic cancer risk.

RESULTS

The study identified 586 cases of pancreatic cancer over a median follow-up period of 7.16 years. In the multivariable-adjusted Cox model, serum GGT level was associated with 14% higher pancreatic cancer risk (hazard ratio (HR) per one standard deviation increment of log2 GGT level = 1.14, 95% confidence interval (CI) 1.02-1.28, p = 0.025). In the total population, the HR for the highest GGT group was 1.68 (95%CI: 1.22-2.30) versus the lowest GGT group. The HR for the highest GGT group in men (≥50.2 U/L) was 1.72 (95%CI: 1.14-2.61) and that in women (≥31.6 U/L) was 1.75 (95%CI: 1.06-2.88) versus the lowest GGT group.

CONCLUSION

Our findings suggested a positive association of serum GGT in pancreatic cancer etiology, implying the potential of monitoring GGT level for identifying at-risk individuals for pancreatic cancer.

The Role of Circulating Protein and Metabolite Biomarkers in the Development of Pancreatic Ductal Adenocarcinoma (PDAC): A Systematic Review and Meta-analysis

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis, and this is attributed to it being diagnosed at an advanced stage. Understanding the pathways involved in initial development may improve early detection strategies. This systematic review assessed the association between circulating protein and metabolite biomarkers and PDAC development.

METHODS

A literature search until August 2020 in MEDLINE, EMBASE, and Web of Science was performed. Studies were included if they assessed circulating blood, urine, or salivary biomarkers and their association with PDAC risk. Quality was assessed using the Newcastle-Ottawa scale for cohort studies. Random-effects meta-analyses were used to calculate pooled relative risk.

RESULTS

A total of 65 studies were included. Higher levels of glucose were found to be positively associated with risk of developing PDAC [n = 4 studies; pooled relative risk (RR): 1.61; 95% CI: 1.16-2.22]. Additionally, an inverse association was seen with pyridoxal 5'-phosphate (PLP) levels (n = 4 studies; RR: 0.62; 95% CI: 0.44-0.87). Meta-analyses showed no association between levels of C-peptide, members of the insulin growth factor signaling pathway, C-reactive protein, adiponectin, 25-hydroxyvitamin D, and folate/homocysteine and PDAC risk. Four individual studies also reported a suggestive positive association of branched-chain amino acids with PDAC risk, but due to differences in measures reported, a meta-analysis could not be performed.

CONCLUSIONS

Our pooled analysis demonstrates that higher serum glucose levels and lower levels of PLP are associated with risk of PDAC.

IMPACT

Glucose and PLP levels are associated with PDAC risk. More prospective studies are required to identify biomarkers for early detection.

Coenzyme Q10 protected against arsenite and enhanced the capacity of 2,3-dimercaptosuccinic acid to ameliorate arsenite-induced toxicity in mice

BACKGROUND

Arsenic poisoning affects millions of people. The inorganic forms of arsenic are more toxic. Treatment for arsenic poisoning relies on chelation of extracellularly circulating arsenic molecules by 2,3-dimecaptosuccinic acid (DMSA). As a pharmacological intervention, DMSA is unable to chelate arsenic molecules from intracellular spaces. The consequence is continued toxicity and cell damage in the presence of DMSA. A two-pronged approach that removes extracellular arsenic, while protecting from the intracellular arsenic would provide a better pharmacotherapeutic outcome. In this study, Coenzyme Q10 (CoQ10), which has been shown to protect from intracellular organic arsenic, was administered separately or with DMSA; following oral exposure to sodium meta-arsenite (NaAsO2) - a very toxic trivalent form of inorganic arsenic. The aim was to determine if CoQ10 alone or when co-administered with DMSA would nullify arsenite-induced toxicity in mice.

METHODS

Group one represented the control; the second group was treated with NaAsO2 (15 mg/kg) daily for 30 days, the third, fourth and fifth groups of mice were given NaAsO2 and treated with 200 mg/kg CoQ10 (30 days) and 50 mg/kg DMSA (5 days) either alone or in combination.

RESULTS

Administration of CoQ10 and DMSA resulted in protection from arsenic-induced suppression of RBCs, haematocrit and hemoglobin levels. CoQ10 and DMSA protected from arsenic-induced alteration of WBCs, basophils, neutrophils, monocytes, eosinophils and platelets. Arsenite-induced dyslipidemia was nullified by administration of CoQ10 alone or in combination with DMSA. Arsenite induced a drastic depletion of the liver and brain GSH; that was significantly blocked by CoQ10 and DMSA alone or in combination. Exposure to arsenite resulted in significant elevation of liver and kidney damage markers. The histological analysis of respective organs confirmed arsenic-induced organ damage, which was ameliorated by CoQ10 alone or when co-administered with DMSA. When administered alone, DMSA did not prevent arsenic-driven tissue damage.

CONCLUSIONS

Findings from this study demonstrate that CoQ10 and DMSA separately or in a combination, significantly protect against arsenic-driven toxicity in mice. It is evident that with further pre-clinical and clinical studies, an adjunct therapy that incorporates CoQ10 alongside DMSA may find applications in nullifying arsenic-driven toxicity.

Risk of gastrointestinal cancer in patients with an elevated level of gamma-glutamyltransferase: A nationwide population-based study

Emerging evidence that an elevated serum gamma-glutamyltransferase (GGT) level is associated with an increased risk of gastrointestinal cancer, but still controversial. The aim of this study to assess the relationship between GGT level and risk of gastrointestinal cancer, and the contribution of the interaction of hyperglycemia with elevated GGT level to the incidence of gastrointestinal cancer by the stratified analysis. A total of 8,120,665 Koreans who received medical checkups in 2009 were included. Subjects were classified according to the quartile of GGT level for women and men. The incidence rates of gastrointestinal cancer for each group were analyzed using Cox proportional hazards models. During follow-up, 129,853 cases of gastrointestinal cancer newly occurred (esophagus, 3,792; stomach, 57,932; and colorectal, 68,789 cases). The highest GGT quartile group showed an increased risk of gastrointestinal cancer (esophagus, hazard ratio = 2.408 [95% confidence interval, 2.184–2.654]; stomach, 1.121 [1.093–1.149]; and colorectal, 1.185 [1.158–1.211]). The risk increased significantly with the rise in GGT quartile level, regardless of the site of cancer. The stratified analysis according to glycemic status showed that the effect of elevated GGT was predominant in the risk of esophageal cancer. The effect of elevated GGT further increased the risk of stomach and colorectal cancers in diabetic patients. An elevated level of GGT was associated with an increased risk of gastrointestinal cancer, regardless of the site of cancer. The effect of the increase in GGT level on the risk of gastrointestinal cancer depended on the type of cancer and glycemic status.

Repeatedly elevated γ-glutamyltransferase levels are associated with an increased incidence of digestive cancers: A population-based cohort study

BACKGROUND

The association between elevated γ-glutamyltransferase (GGT) at a certain point and incident cancer has been suggested; however, no study has evaluated the association between repeatedly elevated GGT and cancer incidence.

AIM

To investigate the effects of repeatedly elevated GGT on the incidence of digestive cancers.

METHODS

Participants who had undergone health screening from 2009 to 2012 and 4 consecutive previous examinations were enrolled. GGT points were calculated as the number of times participants met the criteria of quartile 4 of GGT in four serial measurements (0-4 points). Multivariable Cox proportional hazard regression models were applied.

RESULTS

In total, 3559109 participants were included; among them, 43574 digestive cancers developed during a median of 6.8 years of follow-up. The incidence of total digestive cancers increased in a dose-response manner in men [adjusted hazard ratio (aHR) compared with those with 0 GGT points = 1.28 and 95% confidence interval (CI) = 1.24-1.33 in those with 1 point; aHR = 1.40 and 95%CI = 1.35-1.46 in those with 2 points; aHR = 1.52 and 95%CI = 1.46-1.58 in those with 3 points; aHR = 1.88 and 95%CI = 1.83-1.94 in those with 4 points; P for trend < 0.001]. This trend was more prominent in men than in women and those with healthy habits (no smoking, no alcohol consumption, and a low body mass index) than in those with unhealthy habits.

CONCLUSION

Repeatedly elevated GGT levels were associated with an increased risk of incident digestive cancer in a dose-responsive manner, particularly in men and those with healthy habits. Repeated GGT measurements may be a good biomarker of incident digestive cancer and could help physicians identify high-risk populations.

Circulating liver function markers and colorectal cancer risk: A prospective cohort study in the UK Biobank

Evidence links the liver to development of colorectal cancer (CRC). However, it remains unknown how liver function may influence CRC risk in the general population. We conducted a prospective cohort study in the UK Biobank of 375 693 participants who provided blood samples in 2006 to 2010. Circulating levels of liver function markers (alanine transaminase [ALT], aspartate transaminase [AST], total bilirubin [TBIL], gamma glutamyltransferase [GGT], alkaline phosphatase [ALP], total protein [TP] and albumin [ALB]) were measured. Incident cancer cases were identified through linkage to the national cancer registry up to 2019. Repeated biomarker measurements were available from a subset of 11 320 participants who were re-assessed in 2012 to 2013. After a median follow-up of 10.0 years, we documented 2662 cases of CRC. Circulating levels of ALT, AST, TBIL, GGT, TP and ALB at baseline were inversely associated with CRC risk (P < .01), with multivariable hazard ratio (95% confidence interval) comparing decile 10 vs 1 of 0.62 (0.51-0.75), 0.63 (0.53-0.75), 0.85 (0.72-1.02), 0.74 (0.61-0.89), 0.70 (0.59-0.84) and 0.66 (0.55-0.79), respectively. Strengthened associations were found after recalibration for repeated measurements. The associations appeared stronger for proximal colon cancer than distal colon cancer and rectal cancer, but consistent for early-, mid- and late-onset CRC. In a large cohort of general population, the UK Biobank, higher circulating levels of ALT, AST, TBIL, GGT, TP and ALB, largely within the normal range, were associated with a lower risk of CRC. The findings support a link between liver function and CRC, and may spur future research on the gut-microbiota-liver axis.

Associations between metabolites and pancreatic cancer risk in a large prospective epidemiological study

OBJECTIVE

To assess whether prediagnostic metabolites were associated with incident pancreatic ductal adenocarcinoma (PDAC) in a prospective cohort study.

DESIGN

We conducted an untargeted analysis of 554 known metabolites measured in prediagnostic serum (up to 24 years) to determine their association with incident PDAC in a nested case-control study of male smokers (372 matched case-control sets) and an independent nested case-control study that included women and non-smokers (107 matched sets). Metabolites were measured using Orbitrap Elite or Q-Exactive high-resolution/accurate mass spectrometers. Controls were matched to cases by age, sex, race, date of blood draw, and follow-up time. We used conditional logistic regression adjusted for age to calculate ORs and 95% CIs for a 1 SD increase in log-metabolite level separately in each cohort and combined the two ORs using a fixed-effects meta-analysis.

RESULTS

Thirty-one metabolites were significantly associated with PDAC at a false discovery rate <0.05 with 12 metabolites below the Bonferroni-corrected threshold (p<9.04×10^-5). Similar associations were observed in both cohorts. The dipeptides glycylvaline, aspartylphenylalanine, pyroglutamylglycine, phenylalanylphenylalanine, phenylalanylleucine and tryptophylglutamate and amino acids aspartate and glutamate were positively while the dipeptides tyrosylglutamine and α-glutamyltyrosine, fibrinogen cleavage peptide DSGEGDFXAEGGGVR and glutathione-related amino acid cysteine-glutathione disulfide were inversely associated with PDAC after Bonferroni correction. Five top metabolites demonstrated significant time-varying associations (p<0.023) with the strongest associations observed 10-15 years after participants' blood collection and attenuated thereafter.

CONCLUSION

Our results suggest that prediagnostic metabolites related to subclinical disease, γ-glutamyl cycle metabolism and adiposity/insulin resistance are associated with PDAC.

Blood biomarkers for early diagnosis of oesophageal cancer: a systematic review

BACKGROUND

Oesophageal cancer prognosis remains poor owing to the inability to detect the disease at an early stage. Nontissue (serum, urinary or salivary) biomarkers potentially offer less invasive methods to aid early detection of oesophageal cancer. We aimed to systematically review studies assessing the relationship between nontissue biomarkers and subsequent development of oesophageal cancer.

METHODS

Using terms for biomarkers and oesophageal cancer, Medline, EMBASE and Web of Science were systematically searched for longitudinal studies, published until April 2016, which assessed the association between nontissue biomarkers and subsequent oesophageal cancer risk. Random effects meta-analyses were used to calculate pooled relative risk (RR) and 95% confidence intervals (CIs), where possible.

RESULTS

A total of 39 studies were included. Lower serum pepsinogen I concentrations were associated with an increased risk of oesophageal squamous cell carcinoma (n=3 studies, pooled RR=2.20, 95% CI: 1.31-3.70). However, the association for the pepsinogen I : II ratio was not statistically significant (n=3 studies, pooled RR=2.22, 95% CI: 0.77-6.40), with a large degree of heterogeneity observed (I=68.0%). Higher serum glucose concentrations were associated with a modestly increased risk of total oesophageal cancer (n=3 studies, pooled RR=1.27, 95% CI: 1.02-1.57). No association was observed for total cholesterol and total oesophageal cancer risk (n=3 studies, pooled RR=0.95, 95% CI: 0.58-1.54). Very few studies have assessed other biomarkers for meta-analyses.

CONCLUSION

Serum pepsinogen I concentrations could aid early detection of oesophageal squamous cell carcinoma. More prospective studies are needed to determine the use of other nontissue biomarkers in the early detection of oesophageal cancer.

Elevated serum gamma-glutamyltransferase is associated with an increased risk of oesophageal carcinoma in a cohort of 8,388,256 Korean subjects

Gamma-glutamyltransferase (GGT) is a marker for hepatic injury and alcohol consumption. However, the association of GGT with the risk of oesophageal carcinoma (OC) has not been fully recognized to date. Therefore, this study aimed to determine the association between elevated GGT and OC, by also considering the body mass index (BMI) of the subjects. Clinical data from 8,388,256 Korean individuals, who were aged 40 years and over and who received healthcare check-ups arranged by the national insurance program in 2007 and 2008, were analysed. Newly diagnosed OC was identified using claims data during a median follow-up duration of 8.72 years. During the study period, 6,863 individuals (0.08%) developed OC. We found that there was an increased risk of OC in subjects with serum GGT values >18 IU/L. Furthermore, a BMI <18.5 kg/m² (underweight) was associated with increased OC risk, while a BMI ≥23.0 kg/m² was associated with a reduced OC risk. Individuals who were both underweight and in the highest GGT quartile (≥40 IU/L) had a far greater risk of OC compared to other individuals (hazard ratio: 3.65, 95% confidence interval: 3.10–4.30). In conclusion, increased serum GGT was associated with an increased risk of developing OC in the general Korean population, regardless of age, sex, smoker status, or alcohol consumption.

Gamma-glutamyltransferase and risk of prostate cancer: Findings from the KIHD prospective cohort study

Increased circulating serum gamma-glutamyltransferase (GGT) has been linked with an increased risk of chronic disease outcomes, including overall and several site-specific cancers. However, the relationship of GGT with prostate cancer risk is uncertain. We aimed to assess the prospective association of GGT with risk of prostate cancer. Serum GGT activity was assessed at baseline in the Finnish Kuopio Ischemic Heart Disease prospective cohort of 2,390 men aged 42-61 years without a history of cancer at baseline. We corrected for within-person variability in GGT values using data from repeat measurements taken several years apart. During a median follow-up of 24.6 years, 230 cases of prostate cancer occurred. The age-adjusted regression dilution ratio for log_e GGT was 0.69 [95% confidence interval (CI): 0.63-0.74]. Serum GGT was nonlinearly associated with risk of prostate cancer. In age-adjusted Cox regression analysis, the hazard ratio (95% CIs) for prostate cancer in a comparison of the top quartile versus bottom quartiles 1-3 of GGT values was 1.43 (1.07 to 1.93; p = 0.017), which persisted on adjustment for several established cancer risk factors 1.46 (1.06 to 2.02; p = 0.020). The association remained unchanged on further adjustment for total energy intake, socioeconomic status, physical activity and C-reactive protein. The association did not importantly vary across several clinical subgroups. GGT is positively and independently associated with future risk of prostate cancer in a middle-aged Finnish male population over long-term follow-up. Further research is needed to understand the mechanistic pathways involved and if GGT may have potential relevance in prostate cancer prevention.

γ-Glutamyltransferase and Breast Cancer Risk Beyond Alcohol Consumption and Other Life Style Factors - A Pooled Cohort Analysis

Objective

Elevated γ-Glutamyltransferase serum levels are associated with increased risk of overall cancer incidence and several site-specific malignancies. In the present prospective study we report on the associations of serum γ-Glutamyltransferase with the risk of breast cancer in a pooled population-based cohort considering established life style risk factors.

Methods

Two cohorts were included in the present study, i.e. the Vorarlberg (n = 97,268) and the Malmoe cohort (n = 9,790). Cox proportional hazards regression models were fitted to estimate HRs for risk of breast cancer.

Results

In multivariate analysis adjusted for age, body mass index and smoking status, women with γ-Glutamyltransferase levels in the top quartile were at significantly higher risk for breast cancer compared to women in the lowest quartile (HR 1.21, 95% CI 1.09 to 1.35; p = 0.005). In the subgroup analysis of the Malmoe cohort, γ-Glutamyltransferase remained an independent risk factor for breast cancer when additionally considering alcohol intake. A statistically significant increase in risk was seen in women with γ-Glutamyltransferase-levels in the top versus lowest quartile in a multivariate model adjusted for age, body mass index, smoking status, physical activity, parity, oral contraceptive-use and alcohol consumption (HR 1.37, 95% CI 1.11–1.69, p = 0.006).

Conclusion

Our findings identified γ-Glutamyltransferase as an independent risk factor for breast cancer beyond the consumption of alcohol and other life style risk factors.

Metabolic serum biomarkers for the prediction of cancer: a follow-up of the studies conducted in the Swedish AMORIS study

The Swedish Apolipoprotein MOrtality RISk study (AMORIS) contains information on more than 500 biomarkers collected from 397,443 men and 414,630 women from the greater Stockholm area during the period 1985–1996. Using a ten-digit personal identification code, this database has been linked to Swedish national registries, which provide data on socioeconomic status, vital status, cancer diagnosis, comorbidity, and emigration. Within AMORIS, 18 studies assessing risk of overall and site-specific cancers have been published, utilising a range of serum markers representing glucose and lipid metabolism, immune system, iron metabolism, liver metabolism, and bone metabolism. This review briefly summarises these findings in relation to more recently published studies and provides an overview of where we are today and the challenges of observational studies when studying cancer risk prediction.

Overall, more recent observational studies supported previous findings obtained in AMORIS, although no new results have been reported for serum fructosamine and inorganic phosphate with respect to cancer risk. A drawback of using serum markers in predicting cancer risk is the potential fluctuations following other pathological conditions, resulting in non-specificity and imprecision of associations observed. Utilisation of multiple combination markers may provide more specificity, as well as give us repeated instead of single measurements. Associations with other diseases may also necessitate further analytical strategies addressing effects of serum markers on competing events in addition to cancer. Finally, delineating the role of serum metabolic markers may generate valuable information to complement emerging clinical studies on preventive effects of drugs and supplements targeting metabolic disorders against cancer.

γ-Glutamyltransferase and cancer risk: The Korean cancer prevention study

Elevated serum γ-glutamyltransferase (GGT) is a marker of hepatic injury and is associated with risk of chronic disease. However, the value of GGT as a biomarker for cancer risk remains unclear. Therefore, we evaluated the association of serum GGT with cancer incidence among more than 1.6 million Koreans. We included 1,662,087 Koreans (1,108,121 men and 553,966 women aged 20-95 years) who received health insurance from the National Health Insurance Service and had a biennial medical evaluation between 1995 and 1998. Follow-up was through December 2012. Using Cox proportional hazards models, we adjusted for age, smoking status, alcohol consumption, exercise and body mass index after exclusion of early cases (cancer diagnosis or death within 5 years of starting follow-up) and estimated hazard ratios (HRs) of overall and organ-specific cancer incidence by GGT quintiles. During the 17-year follow-up, 129,087 new cancer cases occurred among the participants. Across levels of GGT, there was a positive gradient of HR and the highest quintile of GGT (≥ 60 IU/L) had the highest HR for all cancers in both men and women. By cancer site, the association was strongest for liver cancer, comparing the highest and lowest strata in men [HR, 6.67; 95% confidence interval (95%CI), 5.88-7.57] and in women (HR, 7.57; 95%CI, 6.41-8.94). Significant associations were also observed for cancers of the esophagus, larynx, stomach, colorectal, bile duct and lung in men and of the bile duct in women. Increased serum GGT level is independently associated with risk of cancer.

Preoperative serum markers for individual patient prognosis in stage I-III colon cancer

Carcinoembryonic antigen (CEA) remains the only recommended biomarker for follow-up care of colorectal cancer (CRC), but besides CEA, several other serological parameters have been proposed as prognostic markers for CRC. The present retrospective analysis investigates a comprehensive set of serum markers with regard to cancer-specific survival (CSS) and disease-free survival (DFS). A total of 472 patients with colon cancer underwent surgery for curative intent between January 1988 and June 2007. Preoperative serum was analyzed for the following parameters: albumin, alkaline phosphatase (aP), beta-human chorionic gonadotropin (βhCG), bilirubin, cancer antigen 125 (CA 125), cancer antigen 19-9 (CA 19-9), CA 72-4, CEA, C-reactive protein (CRP), cytokeratin-19 soluble fragment (CYFRA 21-1), ferritin, gamma-glutamyltransferase (γGT), glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), hemoglobin, haptoglobin, interleukin-6, interleukin-8, creatinine, lactate dehydrogenase (LDH), serum amyloid A (SAA), and 25-hydroxyvitamin D. After a median follow-up period of 5.9 years, the overall 3- and 5-year CSS was 91.7 and 84.9 % and DFS rates were 82.7 % (3 years) and 77.6 % (5 years). Multivariate analyses confirmed preoperative CEA as an independent prognostic factor with regard to CSS and DFS. CA 19-9 and γGT also provided prognostic value for CSS and DFS, respectively. Younger age was negatively associated with DFS. According to UICC stage, CEA provided significant prognostic value with regard to CSS and DFS, while CA 19-9 was only prognostic for CSS. Combined analysis is able to identify patients with favorable prognosis. In addition to tumor baseline parameters, preoperative CEA could be confirmed as prognostic marker in colon cancer. CA 19-9 and γGT also provide additional prognostic value with regard to survival and recurrence in stage III and stage I disease, respectively. The combined use of CEA together with CA 19-9 and γGT improve risk-adapted post-op surveillance.

Gamma glutamyltransferase, alanine aminotransferase and risk of cancer: systematic review and meta-analysis

The prospective evidence for the associations of gamma glutamyltransferase (GGT) and alanine aminotransferase (ALT) with risk of cancer in the general population is uncertain. We conducted a systematic review and meta-analysis of published prospective observational studies evaluating the associations of baseline levels of GGT and ALT with risk of overall (incidence and/or mortality) and site-specific cancers. Relevant studies were identified in a literature search of MEDLINE, EMBASE, Web of Science, reference lists of relevant studies to April 2014 and email contact with investigators. Study specific relative risks (RRs) were meta-analyzed using random effects models. Fourteen cohort studies with data on 1.79 million participants and 57,534 cancer outcomes were included. Comparing top versus bottom thirds of baseline circulating GGT levels, pooled RRs (95% confidence intervals) were 1.32 (1.15-1.52) for overall cancer, 1.09 (0.95-1.24) for cancers of the breast and female genital organs, 1.09 (1.02-1.16) for cancers of male genital organs, 1.94 (1.35-2.79) for cancers of digestive organs and 1.33 (0.94-1.89) for cancers of respiratory and intrathoracic organs. For ALT, corresponding RRs for overall cancer were 0.96 (0.94-0.99) and 1.65 (1.52-1.79) in European and Asian populations, respectively. There was an increased risk of cancers of the digestive organs 2.44 (1.23-4.84). The pooled RR for overall cancer per 5 U/L increment in GGT levels was 1.04 (1.03-1.05). Available observational data indicate a positive log-linear association of GGT levels with overall cancer risk. The positive association was generally evident for site-specific cancers. There are geographical variations in the association of ALT and overall cancer.