Body mass index change during adulthood and risk of oesophageal squamous-cell carcinoma in a Japanese population: the Japan Public Health (JPHC)-based prospective study

Adiposity and risks of gastrointestinal cancers: A 10-year prospective study of 0.5 million Chinese adults

Associations of adiposity with risks of oesophageal squamous cell carcinoma (ESCC) and non-cardia stomach cancer, both prevalent in China, are still inconclusive. While adiposity is an established risk factor for colorectal cancer, the relevance of fat-free mass and early-adulthood adiposity remains to be explored. The prospective China Kadoorie Biobank study included 0.5 million adults (aged 30-79 years) from 10 areas in China. Participants' body size and composition were measured at baseline and at resurveys (amongst a subset). After >10 years of follow-up, 2350, 3345 and 3059 incident cases of oesophageal (EC), stomach (SC) and colorectal (CRC) cancers were recorded, respectively. Cox regression was used to estimate hazard ratios (HRs) for these cancers in relation to different adiposity traits. General and central adiposity were inversely associated with EC (primarily ESCC) risk, with HRs of 0.81 (95% CI 0.77-0.85), 0.76 (0.72-0.81) and 0.87 (0.83-0.92) per SD increase in usual levels of BMI, body fat percentage (BF%) and waist circumference (WC), respectively. Adiposity was also inversely associated with SC risk [HR = 0.79 (0.75-0.83) and 0.88 (0.84-0.92) per SD increase in usual BF% and WC], with heterogeneity by cardia and non-cardia subsites, and positively associated with CRC [HR = 1.09 (1.03-1.15) and 1.17 (1.12-1.22) per SD higher usual BF% and WC]. Fat-free mass was inversely associated with EC [HR = 0.93 (0.89-0.98) per SD increase] but positively associated with CRC [1.09 (1.04-1.14)], while BMI at age 25 was positively associated with all three cancers. After mutual adjustment, general adiposity remained inversely associated with EC and SC, while central adiposity remained positively associated with CRC.

Body mass index trajectories and mortality risk in Japan using a population-based prospective cohort study: the Japan Public Health Center-based Prospective Study

BACKGROUND

Recent studies have found that long-term changes in weight during adulthood are associated with a high risk of mortality. The objective of this study was to characterize body mass index (BMI) trajectories during adulthood and to examine the association between BMI trajectories and risk of death in the Japanese population.

METHODS

The data were extracted from Japan Public Health Center-based Prospective Study-a population-based prospective cohort study in Japan with participants aged 40-69 years followed over 20 years. The participants were categorized into multiple BMI trajectory groups using the latent class growth model. The Cox proportional-hazards model was conducted using all-cause mortality and cause-specific mortality as outcomes and the identified BMI trajectory groups as a predictor. In total, 65 520 participants were included in the analysis.

RESULTS

Six BMI trajectory groups were identified: underweight stable (Group 1), low-to-high normal (Group 2), high-to-low normal (Group 3), normal to overweight (Group 4), overweight to normal (Group 5) and normal to obese (Group 6). Our Cox models showed a higher hazard (risk) of all-cause mortality among participants in the BMI-declining groups [Group 3, adjusted hazard ratio (aHR): 1.10, 95% CI: 1.05-1.16; Group 5, aHR: 1.16, 95% CI: 1.08-1.26], underweight stable group (Group 1, aHR: 1.27, 95% CI: 1.21-1.33) and normal to obese group (Group 6, aHR: 1.22, 95% CI: 1.13-1.33) than Group 2 (low-to-high normal BMI trajectory).

CONCLUSIONS

Stable underweight and weight loss were associated with a high risk of mortality, both of which were uniquely observed in a Japanese population.

Body mass index and esophageal and gastric cancer: A pooled analysis of 10 population-based cohort studies in Japan

The effect of body mass index (BMI) on esophageal and gastric carcinogenesis might be heterogeneous, depending on subtype or subsite. However, findings from prospective evaluations of BMI associated with these cancers among Asian populations have been inconsistent and limited, especially for esophageal adenocarcinoma and gastric cardia cancer. We performed a pooled analysis of 10 population-based cohort studies to examine this association in 394,247 Japanese individuals. We used Cox proportional hazards regression to estimate study-specific hazard ratios (HRs) and 95% confidence intervals (CIs), then pooled these estimates to calculate summary HRs with a random effects model. During 5,750,107 person-years of follow-up, 1569 esophageal cancer (1038 squamous cell carcinoma and 86 adenocarcinoma) and 11,095 gastric (728 cardia and 5620 noncardia) cancer incident cases were identified. An inverse association was observed between BMI and esophageal squamous cell carcinoma (HR per 5-kg/m2 increase 0.57, 95% CI 0.50-0.65), whereas a positive association was seen in gastric cardia cancer (HR 1.15, 95% CI 1.00-1.32). A nonsignificant and significant positive association for overweight or obese (BMI ≥25 kg/m2 ) relative to BMI <25 kg/m2 was observed with esophageal adenocarcinoma (HR 1.32, 95% CI 0.80-2.17) and gastric cardia cancer (HR 1.24, 95% CI 1.05-1.46), respectively. No clear association with BMI was found for gastric noncardia cancer. This prospective study-the largest in an Asian country-provides a comprehensive quantitative estimate of the association of BMI with upper gastrointestinal cancer and confirms the subtype- or subsite-specific carcinogenic impact of BMI in a Japanese population.

A Nutrition-Related Factor-Based Risk Stratification for Exploring the Clinical Benefits in the Treatment of Patients With Locally Advanced Esophageal Squamous Cell Carcinoma Receiving Definitive Chemoradiotherapy: A Retrospective Cohort Study

Objective

No study has reported the risk stratification of BMI and PNI in patients with locally advanced esophageal squamous cell carcinoma (ESCC) undergoing definitive chemoradiotherapy (dCRT). This study aimed to construct a risk stratification to guide the treatment of ESCC following dCRT.

Methods

A total of 1,068 patients with locally advanced ESCC who received dCRT were retrospectively analyzed. The impacts of clinicopathological factors on overall survival (OS) and progression-free survival (PFS) were analyzed. Besides, the novel prognostic indices of pre-therapeutic nutritional index (PTNI) and prognostic index (PI) were developed.

Results

The median follow-up period of OS and PFS were 22.9 and 17.4 months, respectively. The high body mass index (BMI) group had better 5-year OS and PFS (36.4 and 34.0%) than the low BMI group (18.8 and 17.2%). The high prognostic nutritional index (PNI) group also had better 5-year OS and PFS (33.4 and 30.9%) than the low PNI group (17.5 and 17.2%). Multivariate Cox regression analysis showed that BMI and PNI were independent prognostic factors for OS and PFS. Based on nutritional indices, patients were categorized into the low-risk (PTNI = 1), medium-risk (PTNI = 2), and high-risk (PTNI = 3) groups with 5-year OS rates of 38.5, 18.9, 17.5%, respectively (p < 0.001) and 5-year PFS rates of 35.8, 17.6, 16.8%, respectively (p < 0.001). Besides, we also constructed a prognostic index (PI) for OS and PFS which was calculated based on statistically significant factors for predicting OS and PFS. The results revealed that the high-risk group had worse OS and PFS than the low-risk group (p < 0.001). Finally, RCS analysis demonstrated a non-linear relationship between the PNI, BMI, and survival for patients with ESCC. The death hazard of PNI and BMI sharply decreased to 41.8 and 19.7.

Conclusion

The decreased pre-therapeutic BMI and PNI levels were associated with a worse survival outcome. BMI and PNI are readily available and can be used to stratify risk factors for locally advanced ESCC patients undergoing dCRT. The novel risk stratification may help to evaluate patients’ pre-therapeutic status and guide dCRT for locally advanced ESCC patients.

Relation Between Body Mass Index and Dry Eye Disease: The Japan Public Health Center-Based Prospective Study for the Next Generation

OBJECTIVE

To investigate the relation between body mass index (BMI) and dry eye disease (DED).

METHODS

We conducted a cross-sectional questionnaire-based survey in 85,264 Japanese men and women aged 40 to 74 years who participated in the Japan Public Health Center-based Prospective Study for the Next Generation (JPHC-NEXT Study). Dry eye disease was defined as the presence of severe symptoms or clinical diagnosis. A multivariable logistic regression model was used to estimate the odds ratios (ORs) of DED associated with BMI and their two-sided 95% confidence intervals (CIs). We adjusted for age, cohort area, visual display terminal time, smoking status, alcohol intake, education status, income status, as well as history of hormone replacement therapy for women.

RESULTS

Prevalence of DED was 23.4% (n = 19,985; 6,289 men, 13,696 women). Higher BMI was correlated with a lower prevalence of DED in a dose-response fashion, with an adjusted OR of DED (95% CI) per 1 kg/m2 increment of BMI of 0.98 (95% CI: 0.97-0.99) for men and 0.97 (95% CI: 0.97-0.98) for women.

CONCLUSIONS

This large population-based study showed an inverse relationship between BMI and prevalence of DED in a Japanese population. Underestimation of DED is warned, especially for participants with high BMI.

Gender Differences in Obesity-Related Cancers

PURPOSE OF REVIEW

In this review, we summarize the role of obesity in carcinogenesis, providing details on specific cancer sites. Special emphasis is given to gender differences in obesity-related cancers and on the effect of bariatric surgery on cancer risk.

RECENT FINDINGS

Accumulating evidence has highlighted the detrimental role of overweight/obesity in cancer, with almost 55% of cancers diagnosed in women and 24% diagnosed in men considered overweight- and obesity-related cancers. Sufficient data have shown that higher BMI is associated with risk of gynecologic malignancies (mainly breast and endometrial cancers) as well as cancers in sites such as the esophagus (adenocarcinoma), gastric cardia, colon, rectum, liver, gallbladder, pancreas, kidney, thyroid gland, and multiple myeloma. The main mechanisms underlying this relationship include the insulin/IGF1 system, the effect of sex hormones, and adipocytokines. Marked differences may be seen in specific cancer sites when comparing men to women. There is a higher overall incidence of obesity-related cancers among females (endometrial, ovarian, and postmenopausal female breast cancers), whereas cancers that concern both sexes show a higher incidence in males, particularly esophageal adenocarcinoma (male to female ratio: 9: 1 in the USA). Additionally, bariatric surgery has provided evidence of lowering overall cancer risk in patients with morbid obesity. Interestingly, bariatric surgery may lower overall cancer risk in women within the first 5 years after surgery due to the reduced risk of breast and endometrial cancer, and non-Hodgkin lymphoma. Obesity constitutes the base for marked metabolic, hormonal, and inflammatory alterations, including increased cancer risk in both men and women. Implementation of early obesity prevention strategies could ameliorate the continuously increasing incidence of cancer attributed to obesity.

Obesity and incident gastrointestinal cancers: overall body size or central obesity measures, which factor matters?

BMI does not reflect the location or amount of body fat. We aimed to investigate the role of general and central obesity measures in the prediction of incident gastrointestinal cancers. In this analysis of the Golestan Cohort Study, we included 47 586 cancer-free individuals followed for 12.3 years (IQR: 10.5-13.2). We investigated the association of obesity measures including BMI, waist circumference and waist-to-hip ratio (WHR) at enrollment and the incidence of esophageal, gastric, colorectal and pancreatic cancers. Cox proportional hazard models were used to estimate the association between covariates and gastrointestinal cancer risk. We observed no significant associations between obesity measures and incidence of the above-mentioned gastrointestinal cancers in men. In women, BMI, waist circumference and WHR were associated with significant reductions in the risk of esophageal squamous cell carcinoma (ESCC): hazard ratio (HR): 0.67 [95% confidence interval (CI): 0.56-0.81], HR: 0.71 (95% CI: 0.60-0.84) and HR: 0.80 (95% CI: 0.68- 0.94), respectively. In addition, WHR was associated with significantly increased risks for colorectal cancer (HR: 1.39, 95% CI: 1.08-1.78) and gastric cancer (HR: 1.24, 95% CI: 1.01-1.51) in women. In this study, statistically significant associations between obesity measures and incident esophageal, gastric and colorectal cancers were seen in women.

Risk factors for esophageal iodine-unstained lesions and changing trends among Japanese alcohol-dependent men (2003-2018)

Globally, a decreasing incidence of male esophageal squamous cell carcinoma (ESCC) has been observed in recent decades. We evaluated the determinants of esophageal distinct iodine-unstained lesions (DIULs), high-cancer-risk lesions and ESCC, among 3858 Japanese alcohol-dependent men (40-79 years) who underwent chromoendoscopic screening between 2003 and 2018. The initial screening detected DIULs ≥ 5 mm in 541 patients (dysplasia in 319 and SCC in 129) and multiple DIULs in 640. The detection rates for DIULs and chronic atrophic gastritis (CAG), pack-years, and the mean corpuscular volume (MCV) decreased over the course of the study period, while the detection of hiatal hernia and/or columnar-lined esophagus (HH/CLE) and the carriers of inactive heterozygous aldehyde dehydrogenase-2 (ALDH2, rs671) increased. Multiple logistic regression analyses showed that an older age, larger number of pack-years, smaller body mass index, larger MCV, presence of a slow-metabolizing alcohol dehydrogenase-1B genotype (rs1229984), presence of an inactive heterozygous ALDH2 genotype, and more advanced degree of CAG increased the odds ratios (ORs) for DIULs, while the 2008-2013 and 2014-2018 screening periods had lower ORs for DIULs than the 2003-2007 screening period. The presence of HH/CLE decreased the OR for multiple DIULs and was associated with a more proximal location of ESCC. In conclusion, the detection of DIULs in an alcohol-dependent population decreased between 2003 and 2018. In addition to reported determinants of ESCC, CAG and HH/CLE were associated with the risk of DIULs. Enigmatically, however, the decline in the detection of DIULs was not adequately explained by these factors and warrants further research.

Urinary exposure of N-nitrosamines and associated risk of esophageal cancer in a high incidence area in China

Esophageal cancer (EC) is a deadly malignancy worldwide with a high incidence and exhibits unevenly geographic prevalence, which suggests that environmental factors are deeply involved in the development of EC. Although the carcinogenesis of nitrosamines in the esophagus has been identified by tremendous toxicological data, the role of nitrosamines in the genesis of human EC has so far proved inconclusive largely due to a lack of convincing evidences. In this study, urinary nitrosamines in population controls and cases with esophageal precancerous lesions, including reflux esophagitis (RE) accompanying with basal cell hyperplasia (BCH) and dysplasia (DYS), and esophageal squamous cell carcinoma (ESCC) were detected by a SPE-LC-MS/MS method and the associated risk was evaluated. Higher excretion concentrations of N-nitrosomethylethylamine (NMEA) in the RE/BCH patients, NMEA and N-nitrosodibutylamine (NDBA) in the DYS patients, and NMEA, NDBA, N-nitrosopyrrolidine (NPyr) and N-nitrosomorpholine (NMor) in the ESCC patients were observed compared with the controls (p < .05). And with the progression of esophageal lesion, the exposure complexity increased in terms of the categories of nitrosamines. Furthermore, the observed positive associations between the hazardous exposure of NMEA, NDBA and NPyr and the increased risk of ESCC, and between NMEA and NDBA and RE/BCH were established. These findings provided direct evidence to support the hypothesis that exposure to nitrosamines are involved in the carcinogenesis of esophageal epithelia in this high incidence area from the perspective of endogenous exposure assessment. However, discoveries in this study need to be confirmed by systematic researches in the future. And the dose-response relationships, the reference ranges or cutoff values to predict the risks of nitrosamines exposure also need to be defined.

Age-dependent survival impact of body mass index in patients with oesophageal squamous cell carcinoma

BACKGROUND

Patients with oesophageal squamous cell carcinoma (ESCC) generally have distinctive body compositions; being underweight is highly prevalent and sarcopenic obesity is rare. We investigated the survival impacts of body mass index (BMI) in elderly (≥65 years) and non-elderly patients undergoing surgery for ESCC.

METHODS

In total, 379 ESCC patients were retrospectively reviewed. Patients were divided into 3 groups according to BMI; low (<20), medium (20-25) and high (≥25). The skeletal muscle index (SMI) was calculated and its relationship with BMI was analysed. Univariate and multivariate Cox hazards models were applied to determine independent predictors of poor overall survival (OS) and cancer-specific survival (CSS).

RESULTS

The low-, medium- and high-BMI groups included 102 (26.9%), 231 (60.9%) and 46 (12.1%) patients, respectively. High BMI with low SMI was rare (n = 6, 1.6%). Patients with low BMI had significantly poorer OS and CSS than those with high and medium BMI (OS; P < 0.001, CSS; P = 0.003). Notably, OS and CSS curves were well-demarcated by BMI (both P < 0.001) in elderly patients, while not being stratified according to BMI in non-elderly patients (OS; P = 0.08, CSS; P = 0.54). Multivariable analysis revealed low BMI, as well as pStage III disease and non-curative resection, to be independent predictors of poor OS (HR 2.73, P < 0.001) and poor CSS (HR 2.88, P < 0.001) in the elderly group.

CONCLUSIONS

The survival and oncological impacts of low BMI were evident only in elderly patients with ESCC. Our findings highlight the age-dependent significance of BMI in patients with this tumour entity.

Cumulative evidence for the relationship between body mass index and the risk of esophageal cancer: An updated meta-analysis with evidence from 25 observational studies

BACKGROUND AND AIM

A large number of papers reporting the relationships between body mass index (BMI) and esophageal cancer (EC) risk have been published in the past few decades; however, these results are inconsistent. Therefore, we carried out meta-analyses to explore the relationships between BMI and the risk of EC (including esophageal squamous cell carcinoma [ESCC] and esophageal adenocarcinoma [EADC]).

METHODS

We used the Web of Science, PubMed, and Embase to identify all published/online articles before December 30, 2018, which yielded 25 articles eligible for data extraction (including 16,561 cases and 11,954,161 controls), and then pooled the relative risks (RRs) and corresponding 95% confidence intervals (CIs) using random-effects model.

RESULTS

Our study presented that underweight had statistically significant association with the risk of EC (RR = 1.78, 95% CI = 1.48, 2.14, P < 0.001) and ESCC (RR = 1.57, 95% CI = 1.20, 2.06, P = 0.001) when compared with normal weight. Interestingly, both overweight and obesity could increase the risk of EADC (RR = 1.56, 95% CI = 1.42, 1.71, P < 0.001; RR = 2.34, 95% CI = 2.02, 2.70, P < 0.001) while decrease the risk of ESCC (RR = 0.71, 95% CI = 0.60, 0.84, P < 0.001; RR = 0.63, 95% CI = 0.60, 0.84, P = 0.002). Additionally, obesity could increase the risk of EC (RR = 1.51, 95% CI = 1.21, 1.89, P < 0.001).

CONCLUSION

These meta-analyses provide a comprehensive and updated epidemiological evidence to confirm the associations between BMI and EC risk. These findings have public health implications with respect to better control bodyweight and then reduce the occurrence of EC (including ESCC and EADC).

Changing trends in cancer incidence of upper aerodigestive tract and stomach in Japanese alcohol-dependent men (1993-2018)

BACKGROUND

Esophageal squamous cell carcinoma (ESCC), head and neck SCC (HNSCC), and gastric adenocarcinoma (GA) are frequently detected at an early stage using endoscopic screening in Japanese alcohol-dependent men.

METHODS

We performed endoscopic screening with esophageal iodine staining and oropharyngolaryngeal inspection in 7582 Japanese alcohol-dependent men (40-79 years) during 1993-2018, and retrospectively investigated their initial screening results.

RESULTS

The 2008-2018 screening showed lower detection rates for ESCC (2.6% vs 4.0%, P = .0009) and GA (0.5% vs 1.4%, P < .0001) for all age brackets, compared with the 1993-2007 screening. The HNSCC detection rate did not change (1.0% vs 1.1%). Multiple logistic regression analyses showed that the 2008-2018 screening had a reduced OR (95% CI) for ESCC (0.34 [0.25-0.47]) and GA (0.19 [0.10-0.35]), compared with the 1993-2007 screening. The reduction in H pylori infection is probably the main reason for the decrease in GA detection over time. Declining trends in pack-years and gastric atrophy and increasing trends in age and body mass index (BMI) were found over time. The presence of advanced gastric atrophy increased the risk for ESCC as well as GA. The inactive heterozygous aldehyde dehydrogenase-2*1/*2 genotype was a strong risk factor for ESCC, HNSCC, and GA. Fewer pack-years and a larger BMI decreased the ESCC risk. However, these confounders cannot fully explain why the incidence of ESCC has decreased markedly over the recent decade.

CONCLUSIONS

The detection rates of ESCC and GA have markedly decreased during the past decade in the alcohol-dependent population. The enigmatic declining trend of ESCC warrants research on this topic.

Adult height, body mass index change, and body shape change in relation to esophageal squamous cell carcinoma risk: A population-based case-control study in China

The relationship between risk of esophageal squamous cell carcinoma (ESCC) and adult height, changes in individual body mass index (BMI) and body shape is not established. We performed a large population‐based case‐control study, which enrolled a total of 1414 ESCC cases and 1989 controls in a high‐incidence area in China. Using face‐to‐face interview with a structured questionnaire, information on participants' heights, weights, and perceived body shapes at 20 years of age was collected. Additionally, data on weight and perceived body shape among the same participants 10 years prior to ascertainment were collected using the same method. Odd ratios (ORs) of ESCC risk in relation to BMI and body shape were estimated using unconditional logistic regression models. The adjusted results indicated that ESCC risk in adults rapidly rose as height increased, plateauing at 170 cm among men and 157 cm among women. Among participants who were underweight, normal weight, or thinner than body shape 4, body weight loss was associated with increased risk of ESCC, and body weight gain was associated with decreased incidence of ESCC (ORs ranging from 0.40 to 0.76). Notably, however, changes in body weight did not significantly affect ESCC risk among participants who were overweight, obese, or larger than body shape 3. Maintaining a fit body shape and a reasonable BMI is advisable and of vital importance to reduce the risk of ESCC, especially in high‐risk areas.

Endoscopic screening using esophageal iodine staining and genotypes of ADH1B and ALDH2 in Japanese alcohol-dependent women

BACKGROUND

The presence of large or multiple esophageal distinct iodine-unstained lesions (DIULs) is a strong predictor of field cancerization in the upper aerodigestive tract. Several risk factors for DIULs, including genetic polymorphisms of alcohol and aldehyde dehydrogenases (ADH1B, rs1229984; ALDH2, rs671), have been demonstrated in Japanese alcohol-dependent men. However, few evaluations of alcohol-dependent women have been conducted in this field.

METHODS

Using multiple logistic regression models, we investigated the results of screening using esophageal iodine staining and the identification of determinants for esophageal DIULs in 472 Japanese alcohol-dependent women.

RESULTS

DIULs ≥5 mm, multiple DILUs, and both characteristics were observed in 35 (7.4%), 31 (6.6%), and 16 (3.4%) patients, respectively. DIULs ≥5 mm were histologically diagnosed as low-grade intraepithelial neoplasia in 26 patients and superficial squamous cell carcinoma in 9 patients. Although the inactive heterozygous ALDH2*1/*2 genotype was more common (33.3% vs. 11.4%, p = 0.002) in the group with DIULs ≥5 mm than in the group without DIULs ≥5 mm, no significant differences in the results of a questionnaire asking about current and past facial flushing after a glass of beer were seen between the groups with and without DIULs ≥5 mm. When individuals with current or former flushing were assumed to have inactive ALDH2, the sensitivity and specificity of current or former flushing to identify the presence of inactive ALDH2 were 50.0% and 93.5%, respectively; these values were previously reported to be 88% and 92%, respectively, in a Japanese general female population. The low sensitivity in the present study suggests that a lack of alcohol flushing may play a crucial role in the development of alcohol dependence in women with inactive ALDH2. No significant differences in age, usual alcohol consumption, or smoking habits were observed according to ADH1B and ALDH2 genotypes. Multiple logistic regression analyses showed that the slow-metabolizing ADH1B*1/*1 genotype (odds ratio [95% confidence interval], 12.5 [4.82-32.4] and 9.89 [3.50-27.9]), the inactive heterozygous ALDH2*1/*2 genotype (2.94 [1.18-7.38] and 3.79 [1.40-10.3]), a lower body mass index per -1 kg/m2 (1.17 [1.02-1.35] and 1.38 [1.14-1.67]), and a mean corpuscular volume ≥106 fl (3.70 [1.56-8.81] and 3.27 [1.24-8.64]) increased the risk of DIULs ≥5 mm and multiple DIULs, respectively. The combination of ADH1B*1/*1 and ALDH2*1/*2 markedly increased the risk of esophageal DIULs ≥5 mm (39.3 [10.6-146]).

CONCLUSIONS

Japanese alcohol-dependent women shared several common risk factors for esophageal squamous cell neoplasia with alcohol-dependent men, but with considerably different magnitudes.

Adiposity and gastrointestinal cancers: epidemiology, mechanisms and future directions

Excess adiposity is a risk factor for several cancers of the gastrointestinal system, specifically oesophageal adenocarcinoma and colorectal, small intestine, pancreatic, liver, gallbladder and stomach cancers. With the increasing prevalence of obesity in nearly all regions of the world, this relationship could represent a growing source of cancers of the digestive system. Experimental and molecular epidemiological studies indicate important roles for alterations in insulin signalling, adipose tissue-derived inflammation and sex hormone pathways in mediating the association between adiposity and gastrointestinal cancer. The intestinal microbiome, gut hormones and non alcoholic fatty liver disease (NAFLD) also have possible roles. However, important gaps remain in our knowledge. For instance, our understanding of how adiposity throughout the life course is related to the risk of gastrointestinal cancer development and of how obesity influences gastrointestinal cancer prognosis and survival is limited. Nonetheless, the increasing use of state-of-the-art analytical methods (such as omics technologies, Mendelian randomization and MRI) in large-scale epidemiological studies offers exciting opportunities to advance our understanding of the complex relationship between adiposity and gastrointestinal cancers. Here, we examine the epidemiology of associations between obesity and gastrointestinal cancer, explore potential mechanisms underlying these relationships and highlight important unanswered research questions.