Increased risk of colorectal cancer after obesity surgery. Ann Surg. 2013;258:983-988. [PMID: 23470581 DOI: 10.1097/sla.0b013e318288463a]

Bariatric Surgery Is Associated with Lower Concentrations of Fecal Secondary Bile Acids and Their Metabolizing Microbial Enzymes: A Pilot Study

INTRODUCTION

Excess body fat elevates colorectal cancer risk. While bariatric surgery (BRS) induces significant weight loss, its effects on the fecal stream and colon biology are poorly understood. Specifically, limited data exist on the impact of bariatric surgery (BRS) on fecal secondary bile acids (BA), including lithocholic acid (LCA), a putative promotor of colorectal carcinogenesis.

METHODS

This cross-sectional case-control study included 44 patients with obesity; 15 pre-BRS (controls) vs. 29 at a median of 24.1 months post-BRS. We examined the fecal concentrations of 11 BA by liquid chromatography and gene abundance of BA-metabolizing bacterial enzymes through fecal metagenomic sequencing. Differences were quantified using non-parametric tests for BA levels and linear discriminant analysis (LDA) effect size (LEfSe) for genes encoding BA-metabolizing enzymes.

RESULTS

Total fecal secondary BA concentrations trended towards lower levels post- vs. pre-BRS controls (p = 0.07). Individually, fecal LCA concentrations were significantly lower post- vs. pre-BRS (8477.0 vs. 11,914.0 uM/mg, p < 0.008). Consistent with this finding, fecal bacterial genes encoding BA-metabolizing enzymes, specifically 3-betahydroxycholanate-3-dehydrogenase (EC 1.1.1.391) and 3-alpha-hydroxycholanate dehydrogenase (EC 1.1.1.52), were also lower post- vs. pre-BRS controls (LDA of - 3.32 and - 2.64, respectively, adjusted p < 0.0001). Post-BRS fecal BA concentrations showed significant inverse correlations with weight loss, a healthy diet quality, and increased physical activity.

CONCLUSIONS

Concentrations of LCA, a secondary BA, and bacterial genes needed for BA metabolism are lower post-BRS. These changes can impact health and modulate the colorectal cancer cascade. Further research is warranted to examine how surgical alterations and the associated dietary changes impact bile acid metabolism.

Bariatric surgery and diabetes: Current challenges and perspectives

Diabetes mellitus (DM) and obesity have become public issues of global concern. Bariatric surgery for the treatment of obesity combined with type 2 DM has been shown to be a safe and effective approach; however, there are limited studies that have systematically addressed the challenges of surgical treatment of obesity combined with DM. In this review, we summarize and answer the most pressing questions in the field of surgical treatment of obesity-associated DM. I believe that our insights will be of great help to clinicians in their daily practice.

Obesity-related cancer and bariatric surgery: A comprehensive systematic review and meta-analysis protocol

INTRODUCTION

Obesity is a silent pandemic affecting all ages and is a component of metabolic syndrome. Its treatment is conducted by lifestyle and behavioral changes, pharmacological therapy, and when correctly indicated, bariatric surgery. In recent years, the procedures for weight loss have been investigated due to their relationship with the development of many types of cancer. Although many studies have shown that bariatric surgery decreases cancer risk, other researchers observed an increase in this association. Carcinogenesis is affected by many factors, such as age, sex, type of cancer, and the bariatric surgery performed on each patient. This systematic review and meta-analysis protocol aims to clarify the association between the different modalities of bariatric surgery and the risk of cancer development in adult patients with metabolic syndrome.

METHOD AND ANALYSIS

The proposed systematic review and meta-analysis will be reported conforming to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-P) guidelines. This research will include observational studies (case-control and cohort studies) about patients who undergo bariatric surgery due to metabolic syndrome. Will be accepted in any language and any year. Publications without peer review will be excluded from this review. Data will be entered into the Review Manager software (RevMan5.2.3). We extracted or calculated the OR and 95% CI for dichotomous outcomes for each study. In case of heterogeneity (I2>50%), the random-effects model will combine the studies to calculate the OR and 95% CI.

ETHICS AND DISSEMINATION

This study will review the published data; Thus, obtaining ethical approval is unnecessary. The findings of this systematic review will be published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42023432079.

Weight-centric prevention of cancer

Background

The link between excess adiposity and carcinogenesis has been well established for multiple malignancies, and cancer is one of the main contributors to obesity-related mortality. The potential role of different weight-loss interventions on cancer risk modification has been assessed, however, its clinical implications remain to be determined. In this clinical review, we present the data assessing the effect of weight loss interventions on cancer risk.

Methods

In this clinical review, we conducted a comprehensive search of relevant literature using MEDLINE, Embase, Web of Science, and Google Scholar databases for relevant studies from inception to January 20, 2024. In this clinical review, we present systematic reviews and meta-analysis, randomized clinical trials, and prospective and retrospective observational studies that address the effect of different treatment modalities for obesity in cancer risk. In addition, we incorporate the opinions from experts in the field of obesity medicine and oncology regarding the potential of weight loss as a preventative intervention for cancer.

Results

Intentional weight loss achieved through different modalities has been associated with a reduced cancer incidence. To date, the effect of weight loss on the postmenopausal women population has been more widely studied, with multiple reports indicating a protective effect of weight loss on hormone-dependent malignancies. The effect of bariatric interventions as a protective intervention for cancer has been studied extensively, showing a significant reduction in cancer incidence and mortality, however, data for the effect of bariatric surgery on certain specific types of cancer is conflicting or limited.

Conclusion

Medical nutrition therapy, exercise, antiobesity medication, and bariatric interventions, might lead to a reduction in cancer risk through weight loss-dependent and independent factors. Further evidence is needed to better determine which population might benefit the most, and the amount of weight loss required to provide a clinically significant preventative effect.

Incidence of cancer for patients after bariatric surgery: evidence from 33 cohort studies

BACKGROUND

With the rising prevalence of severe obesity, bariatric surgery has emerged as a crucial treatment option. As the number of surgeries performed worldwide increases, there has been growing interest in the impact of bariatric surgery on cancer incidence. While several studies have examined this relationship, the topic remains controversial.

OBJECTIVES

We conducted this systematic review of cohort studies with meta-analysis to evaluate the effect of bariatric surgery versus nonsurgical treatment on overall cancer incidence. However, the effects may vary when focusing on specific cancer types, surgical procedures, or gender, so we conducted additional subgroup analyses.

SETTING

A meta-analysis. University hospital.

METHODS

The Cochrane, Embase, PubMed, and Web of Science databases were searched for studies from 1 January 2000 to 1 December 2022. Meta-analysis was conducted to evaluate the pooled effect and further implemented subgroup analysis stratified by cancer type, operation type, and sex.

RESULTS

All cohort studies were included in this meta-analysis from 18,216 studies. The overall cancer incidence demonstrated a significant decrease in the group with bariatric surgery (odds ratios [OR] = .56, P = .000, 95% CI .46 to .68). In subgroup analysis, similar decrease effect was found in 9 cancers. Furthermore, the incidence of cancer decreased significantly in male (OR = .66, P = .001, 95% CI .51 to .85) and female patients (OR = .63, P = .000, 95% CI .57 to .69) and patients undergoing gastric bypass (OR = .46, P = .000, 95% CI .33 to .63) or sleeve gastrectomy (OR = .44, P = .001, 95% CI .27 to .70).

CONCLUSIONS

In the overall analysis, bariatric surgery could reduce the incidence of cancer significantly. Further large-scale well-matched studies are needed to verify the protective effect of bariatric surgery on cancer incidence.

Impact of RYGB surgery on plasma immunoglobulins: association between blood pressure and glucose levels six months after surgery

We aimed to study levels of natural antibodies in plasma, and their associations to clinical and fecal biomarkers, before and 6 months after Roux-en-Y gastric bypass (RYGB) surgery. Thirty individuals with obesity [16 type 2 diabetic, 14 non-diabetic (ND)] had RYGB surgery. Total plasma IgA, IgG and IgM antibody levels and specific antibodies to oxidized low-density lipoprotein (oxLDL), malondialdehyde-acetaldehyde adducts, Porphyromonas gingivalis gingipain A hemagglutinin domain (Rgp44), and phosphocholine were measured using chemiluminescence immunoassay. Associations between plasma and fecal antibodies as well as clinical markers were analyzed. RYGB surgery reduced blood pressure, and the glycemic state was improved. A higher level of diastolic blood pressure was associated with lower plasma antibodies to oxLDL after surgery. Also, lower level of glucose markers associated with lower level of plasma antibodies to bacterial virulence factors. Antibodies to oxLDL decreased after surgery, and positive association between active serum lipopolysaccharide and specific oxLDL antibodies was detected. Total IgG levels decreased after surgery, but only in ND individuals. Reduced level of total plasma IgG, improved state of hypertension and hyperglycemia and their associations with decreased levels of specific antibodies in plasma, suggest an improved state of systemic inflammation after RYGB surgery.

Bariatric Surgery and Longitudinal Cancer Risk: A Review

Importance

Cancer is one of the leading causes of death in the United States, with the obesity epidemic contributing to its steady increase every year. Recent cohort studies find an association between bariatric surgery and reduced longitudinal cancer risk, but with heterogeneous findings.

Observations

This review summarizes how obesity leads to an increased risk of developing cancer and synthesizes current evidence behind the potential for bariatric surgery to reduce longitudinal cancer risk. Overall, bariatric surgery appears to have the strongest and most consistent association with decreased incidence of developing breast, ovarian, and endometrial cancers. The association of bariatric surgery and the development of esophageal, gastric, liver, and pancreas cancer is heterogenous with studies showing either no association or decreased longitudinal incidences. Conversely, there have been preclinical and cohort studies implying an increased risk of developing colon and rectal cancer after bariatric surgery. A review and synthesis of the existing literature reveals epidemiologic shortcomings of cohort studies that potentially explain incongruencies observed between studies.

Conclusions and Relevance

Studies examining the association of bariatric surgery and longitudinal cancer risk remain heterogeneous and could be explained by certain epidemiologic considerations. This review provides a framework to better define subgroups of patients at higher risk of developing cancer who would potentially benefit more from bariatric surgery, as well as subgroups where more caution should be exercised.

Distinctive patterns of sulfide- and butyrate-metabolizing bacteria after bariatric surgery: potential implications for colorectal cancer risk

Despite improved cardiometabolic outcomes following bariatric surgery, its long-term impact on colorectal cancer (CRC) risk remains uncertain. In parallel, the influence of bariatric surgery on the host microbiome and relationships with disease outcomes is beginning to be appreciated. Therefore, we investigated the impact of Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) on the patterns of sulfide-reducing and butyrate-producing bacteria, which are hypothesized to modulate CRC risk after bariatric surgery. In this single-center, cross-sectional study, we included 15 pre-surgery subjects with severe obesity and patients who are at a median (range) of 25.6 (9.9-46.5) months after RYGB (n = 16) or VSG (n = 10). The DNA abundance of fecal bacteria and enzymes involved in butyrate and sulfide metabolism were identified using metagenomic sequencing. Differences between pre-surgery and post-RYGB or post-VSG cohorts were quantified using the linear discriminant analysis (LDA) effect size (LEfSe) method. Our sample was predominantly female (87%) with a median (range) age of 46 (23-71) years. Post-RYGB and post-VSG patients had a higher DNA abundance of fecal sulfide-reducing bacteria than pre-surgery controls (LDA = 1.3-4.4, p < .05). The most significant enrichments were for fecal E. coli, Acidaminococcus and A. finegoldii after RYGB, and for A. finegoldii, S. vestibularis, V. parvula after VSG. As for butyrate-producing bacteria, R. faecis was more abundant, whereas B. dentium and A. hardus were lower post-RYGB vs. pre-surgery. B. dentium was also lower in post-VSG vs. pre-surgery. Consistent with these findings, our analysis showed a greater enrichment of sulfide-reducing enzymes after bariatric surgery, especially RYGB, vs. pre-surgery. The DNA abundance of butyrate-producing enzymes was lower post-RYGB. In conclusion, the two most used bariatric surgeries, RYGB and VSG, are associated with microbiome patterns that are potentially implicated in CRC risk. Future studies are needed to validate and understand the impact of these microbiome changes on CRC risk after bariatric surgery.

Risk reduction of non-hormonal cancers following bariatric surgery

Metabolic and bariatric surgery (MBS) is the most effective intervention for weight loss leading to significant resolution of obesity-related medical conditions. Recent literature has demonstrated risk reduction of certain cancer types after MBS. Studies have shown an overall reduction in the risk of hormonal cancer, such as breast and endometrial cancer. However, the association between bariatric surgery and the incidence of various types of non-hormonal cancer such as esophageal, gastric, liver, gallbladder, colorectal, pancreatic and kidney cancer remains contested. The aim of this study was to highlight obesity and its relationship to cancer development as well as bariatric surgery and its role in cancer reduction with focus on non-hormonal cancers.

Obesity, obesities and gastrointestinal cancers

Obesity has been recognized to be increasing globally and is designated a disease with adverse consequences requiring early detection and appropriate care. In addition to being related to metabolic syndrome disorders such as type 2 diabetes, hypertension, stroke, and premature coronary artery disease. Obesity is also etiologically linked to several cancers. The non-gastrointestinal cancers are breast, uterus, kidneys, ovaries, thyroid, meningioma, and thyroid. Gastrointestinal (GI) cancers are adenocarcinoma of the esophagus, liver, pancreas, gallbladder, and colorectal. The brighter side of the problem is that being overweight and obese and cigarette smoking are mostly preventable causes of cancers. Epidemiology and clinical studies have revealed that obesity is heterogeneous in clinical manifestations. In clinical practice, BMI is calculated by dividing a person's weight in kilograms by the square of the person's height in square meters (kg/m2). A BMI above 30 kg/m2 (defining obesity in many guidelines) is considered obesity. However, obesity is heterogeneous. There are subdivisions for obesity, and not all obesities are equally pathogenic. Adipose tissue, in particular, visceral adipose tissue (VAT), is endocrine and abdominal obesity (a surrogate for VAT) is evaluated by waist-hip measurements or just waist measures. Visceral Obesity, through several hormonal mechanisms, induces a low-grade chronic inflammatory state, insulin resistance, components of metabolic syndrome, and cancers. Metabolically obese, normal-weight (MONW) individuals in several Asian countries may have BMI below normal levels to diagnose obesity but suffer from many obesity-related complications. Conversely, some people have high BMI but are generally healthy with no features of metabolic syndrome. Many clinicians advise weight loss by dieting and exercise to metabolically healthy obese with large body habitus than to individuals with metabolic obesity but normal BMI. The GI cancers (esophagus, pancreas, gallbladder, liver, and colorectal) are individually discussed, emphasizing the incidence, possible pathogenesis, and preventive measures. From 2005 to 2014, most cancers associated with overweight and Obesity increased in the United States, while cancers related to other factors decreased. The standard recommendation is to offer or refer adults with a body mass index (BMI) of 30 or more to intensive, multicomponent behavioral interventions. However, the clinicians have to go beyond. They should critically evaluate BMI with due consideration for ethnicity, body habitus, and other factors that influence the type of obesity and obesity-related risks. In 2001, the Surgeon General's ``Call to Action to Prevent and Decrease Overweight and Obesity'' identified obesity as a critical public health priority for the United States. At government levels reducing obesity requires policy changes that improve the food and physical activity for all. However, implementing some policies with the most significant potential benefit to public health is politically tricky. The primary care physician, as well as subspecialists, should identify overweight and Obesity based on all the variable factors in the diagnosis. The medical community should address the prevention of overweight and Obesity as an essential part of medical care as much as vaccination in preventing infectious diseases at all levels- from childhood, to adolescence, and adults.

Bariatric surgery reduces colorectal cancer incidence in obese individuals: Systematic review and meta-analysis

BACKGROUND

Colorectal cancer ranks third in global cancer prevalence and stands as the second leading cause of cancer-related mortalities. With obesity recognized as a pivotal risk factor for colorectal cancer, the potential protective role of bariatric surgery, especially laparoscopic Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy, has garnered attention.

AIM

To investigate the Roux-en-Y gastric bypass (RYGB) vs sleeve gastrectomy (SG) effect on colorectal cancer incidence in obese individuals.

METHODS

A systematic review and meta-analysis of the literature was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Seventeen studies with a total of 12497322 patients were included. The primary outcome was the relative risk (RR) of developing colorectal cancer in obese patients who underwent weight loss surgery compared to those who did not. Secondary outcomes included determining the RR for colon and rectal cancer separately and subgroup analyses by gender and type of weight loss surgery.

RESULTS

The meta-analysis revealed a 54% reduction in colorectal cancer risk in morbidly obese patients who underwent bariatric surgery compared to those who did not. A significant 46% reduction in colorectal cancer risk was observed among female patients. However, no significant differences were found in the meta-analysis for various types of bariatric surgery, such as SG and RYGB.

CONCLUSION

This meta-analysis reveals weight loss surgery, regardless of type, reduces colorectal cancer risk, especially in women, as indicated by RR and hazard ratio assessments. Further validation is essential.

Systemic adiponectin levels in colorectal cancer and adenoma: a systematic review and meta-analysis

BACKGROUND

Obesity is a well-established risk factor in the development of colorectal cancer; however, the mechanism mediating this relationship is not well understood. The adipokine, adiponectin, has an inverse relationship with obesity. Experimental studies have shown adiponectin to have dichotomous inflammatory and tumorigenic roles. Its role in the development of colorectal cancer, including the potential effect of its increase following bariatric surgery, is not yet clear. There are conflicting results from studies evaluating this relationship. This study sought to provide a systematic review and meta-analysis to examine the association between systemic adiponectin levels in patients with colorectal cancer and adenoma.

METHODS

An electronic literature search was performed using PubMed, EMBASE, Web of Science as well as gray literature. Articles were screened for inclusion criteria and assessed for quality using the Newcastle-Ottawa Scale. Pooled mean differences were calculated using a random effects model. Subgroup and meta-regression analyses were performed to identify potential sources of heterogeneity.

RESULTS

Thirty-two observational studies comparing systemic adiponectin in colorectal cancer vs healthy controls were included. Colorectal cancer cases had lower systemic adiponectin levels (overall pooled mean difference = -1.05 μg/ml [95% CI: -1.99; -0.12] p = 0.03); however, significant heterogeneity was present (I2 = 95% p < 0.01). Subgroup and meta- regression analyses results could not identify a source of the significant heterogeneity across the studies.

CONCLUSIONS

Studies suggest a trend towards lower systemic adiponectin levels in colorectal cancer patients, but the heterogeneity observed showed current evidence is not sufficient to definitively draw any conclusions. These data, however, suggest rising adiponectin is unlikely to account for the reported observation of increased CRC following bariatric surgery. Further studies with prospective age, race, and BMI-matched cohorts, and standardized adiponectin measurements may provide a better understanding of this relationship.

The Impact of Bariatric Surgery on the Incidence of Colorectal Cancer in Patients with Obesity-a Systematic Review and Meta-analysis of Registry Data

PURPOSE

Cancer and obesity represent two of the most significant global health concerns. The risk of malignancy, including colorectal cancer (CRC), increases with obesity. The aim of this study was to perform a systematic review and meta-analysis to determine the value of bariatric surgery in reducing CRC risk in patients with obesity using registry data.

MATERIALS AND METHODS

A systematic review and meta-analysis were performed as per PRISMA guidelines. The risk of CRC was expressed as a dichotomous variable and reported as odds ratios (OR) with 95% confidence intervals (CIs) using the Mantel-Haenszel method. A multi-treatment comparison was performed, examining the risk reduction associated with existing bariatric surgery techniques. Analysis was performed using RevMan, R packages, and Shiny.

RESULTS

Data from 11 registries including 6,214,682 patients with obesity were analyzed. Of these, 14.0% underwent bariatric surgery (872,499/6,214,682), and 86.0% did not undergo surgery (5,432,183/6,214,682). The mean age was 49.8 years, and mean follow-up was 5.1 years. In total, 0.6% of patients who underwent bariatric surgery developed CRC (4,843/872,499), as did 1.0% of unoperated patients with obesity (54,721/5,432,183). Patients with obesity who underwent bariatric surgery were less likely to develop CRC (OR: 0.53, 95% CI: 0.36-0.77, P < 0.001, I2 = 99%). Patients with obesity undergoing gastric bypass surgery (GB) (OR: 0.513, 95% CI: 0.336-0.818) and sleeve gastrectomy (SG) (OR: 0.484, 95% CI: 0.307-0.763) were less likely to develop CRC than unoperated patients.

CONCLUSION

At a population level, bariatric surgery is associated with reduced CRC risk in patients with obesity. GB and SG are associated with the most significant reduction in CRC risk.

PROSPERO REGISTRATION

CRD42022313280.

Impact of bariatric surgery on early-onset colorectal cancer risk: a systematic review and meta-analysis

The aim of this meta-analysis is to determine the impact of bariatric surgery on the risk of early-onset colorectal neoplasia. This systematic review was conducted according to PRISMA recommendations. It was registered in the PROSPERO international database. A comprehensive search was conducted in electronic databases (MEDLINE, EMBASE, and Web of Science) for completed studies until May 2022. The Search was made using a mixture of indexed terms and title, abstract and keywords. The search included terms: obese, surgical weight loss intervention, colorectal cancer, and colorectal adenomas. Studies that included bariatric intervention patient's vs non-surgical obese patients younger than 50 years were considered. Inclusion criteria were patients with BMI more than 35 kg/m² who underwent a colonoscopy. Studies with follow-up colonoscopy performed in less than 4 years after bariatric surgery and those that evaluated patients with a mean age difference of 5 or more years between groups were excluded. Outcomes analyzed in obese patients with surgical treatment vs control patients included colorectal cancer incidence. From 2008 to 2021, a total of 1536 records were identified. Five retrospective studies that included 48,916 patients were analyzed. Follow-up period ranged from 5 to 22.2 years. 20,663 (42.24%) patients underwent bariatric surgery and 28,253 (57.76%) were part of the control patients. Roux-en-Y gastric bypass was performed in 14,400 (69.7%) individuals. The intervention and control group were similar in age range, proportion of female participants and initial body mass index (35-48.3 vs 35-49.3, respectively). 126/20663 (0.61%) patients in the bariatric surgery group and 175/28253 (0.62%) individuals in the control group presented CRC. In this meta-analysis, we were unable to demonstrate a significant impact of the Bariatric Surgery on EOCRC risk. Prospective trials with longer follow-up periods should be done to prove the colorectal cancer risk reduction.

The impact of surgical weight loss procedures on the risk of metachronous colorectal neoplasia: the differential effect of surgery type, sex, and anatomic location

Patients with prior colorectal polyps are at high risk for metachronous colorectal neoplasia, especially in the presence of obesity. We assessed the impact of 2 common bariatric surgeries, vertical sleeve gastrectomy and roux-n-Y gastric bypass, on the risk of colorectal neoplasia recurrence. This nationally representative analysis included 1183 postbariatric adults and 3193 propensity score-matched controls, who all had prior colonoscopy with polyps and polypectomy. Colorectal polyps reoccurred in 63.8% of bariatric surgery patients and 71.7% of controls at a mean follow-up of 53.1 months from prior colonoscopy. There was a reduced odds of colorectal polyp recurrence after bariatric surgery compared with controls (odds ratio [OR] = 0.70, 95% confidence interval [CI] = 0.58 to 0.83). This effect was most pronounced in men (OR = 0.58, 95% CI = 0.42 to 0.79), and post roux-n-Y gastric bypass (OR = 0.57, 95% CI = 0.41 to 0.79). However, the risk of rectal polyps or colorectal cancer remained consistent between groups. This study is the first to our knowledge to show a reduction in risk of polyp recurrence following bariatric surgery.

Metabolic and bariatric surgery and obesity pharmacotherapy for cancer prevention: current status and future possibilities

Obesity is a chronic, relapsing, progressive disease of excess adiposity that increases the risk of developing at least 13 types of cancer. This report provides a concise review of the current state of the science regarding metabolic and bariatric surgery and obesity pharmacotherapy related to cancer risk. Meta-analyses of cohort studies report that metabolic and bariatric surgery is independently associated with a lower risk of incident cancer than nonsurgical obesity care. Less is known regarding the cancer-preventive effects of obesity pharmacotherapy. The recent approval and promising pipeline of obesity drugs will provide the opportunity to understand the potential for obesity therapy to emerge as an evidence-based cancer prevention strategy. There are myriad research opportunities to advance our understanding of how metabolic and bariatric surgery and obesity pharmacotherapy may be used for cancer prevention.

Obesity, the Adipose Organ and Cancer in Humans: Association or Causation?

Epidemiological observations, experimental studies and clinical data show that obesity is associated with a higher risk of developing different types of cancer; however, proof of a cause-effect relationship that meets the causality criteria is still lacking. Several data suggest that the adipose organ could be the protagonist in this crosstalk. In particular, the adipose tissue (AT) alterations occurring in obesity parallel some tumour behaviours, such as their theoretically unlimited expandability, infiltration capacity, angiogenesis regulation, local and systemic inflammation and changes to the immunometabolism and secretome. Moreover, AT and cancer share similar morpho-functional units which regulate tissue expansion: the adiponiche and tumour-niche, respectively. Through direct and indirect interactions involving different cellular types and molecular mechanisms, the obesity-altered adiponiche contributes to cancer development, progression, metastasis and chemoresistance. Moreover, modifications to the gut microbiome and circadian rhythm disruption also play important roles. Clinical studies clearly demonstrate that weight loss is associated with a decreased risk of developing obesity-related cancers, matching the reverse-causality criteria and providing a causality correlation between the two variables. Here, we provide an overview of the methodological, epidemiological and pathophysiological aspects, with a special focus on clinical implications for cancer risk and prognosis and potential therapeutic interventions.

The effect of bariatric surgery on reducing the risk of colorectal cancer: a meta-analysis of 3,233,044 patients

BACKGROUND

The published literature presents conflicting results regarding the impact of bariatric surgery on the incidence of colorectal cancer. There are important new studies that have addressed this question with longer follow-up.

OBJECTIVE

To investigate the effect of bariatric surgery on the risk of developing colorectal cancer in patients with obesity.

SETTING

Meta-analysis.

METHODS

PubMed and Scopus were searched for relevant articles. Articles published by November 2021 were retrieved; data were extracted according to the evidence-based PICO (population, intervention, control, outcome) model and analyzed using a random-effects model to estimate the pooled relative risk (RR) and its 95% confidence interval. The heterogeneity of studies was tested and quantified using Cochran's Q.

RESULTS

The initial search yielded 327 articles. After evaluation, 13 studies were analyzed. The thorough evaluation resulted in 13 articles, which were analyzed. A total number of 3,233,044 patients were included in the meta-analysis. The mean time of follow-up was 9.5 ± 7.9 years. The pooled estimate of the adjusted RR was .63 (95% confidence interval, .50-.79). Heterogeneity χ² was 107.96 (df = 12; P < .001; I² = 89%).

CONCLUSION

Patients who underwent bariatric surgery had a 37% reduction in the risk of developing colorectal cancer compared with patients with obesity who had no surgery.

Systematic Review and Meta-Analysis of the Impact of Bariatric Surgery on Future Cancer Risk

The study aimed to perform a systematic review and meta-analysis of the evidence for the prevention of future cancers following bariatric surgery. A systematic literature search of the Cochrane Library, Embase, Scopus, Web of Science and PubMed databases (2007–2023), Google Scholar and grey literature was conducted. A meta-analysis was performed using the inverse variance method and random effects model. Thirty-two studies involving patients with obesity who received bariatric surgery and control patients who were managed with conventional treatment were included. The meta-analysis suggested bariatric surgery was associated with a reduced overall incidence of cancer (RR 0.62, 95% CI 0.46–0.84, p < 0.002), obesity-related cancer (RR 0.59, 95% CI 0.39–0.90, p = 0.01) and cancer-associated mortality (RR 0.51, 95% CI 0.42–0.62, p < 0.00001). In specific cancers, bariatric surgery was associated with reduction in the future incidence of hepatocellular carcinoma (RR 0.35, 95% CI 0.22–0.55, p < 0.00001), colorectal cancer (RR 0.63, CI 0.50–0.81, p = 0.0002), pancreatic cancer (RR 0.52, 95% CI 0.29–0.93, p = 0.03) and gallbladder cancer (RR 0.41, 95% CI 0.18–0.96, p = 0.04), as well as female specific cancers, including breast cancer (RR 0.56, 95% CI 0.44–0.71, p < 0.00001), endometrial cancer (RR 0.38, 95% CI 0.26–0.55, p < 0.00001) and ovarian cancer (RR 0.45, 95% CI 0.31–0.64, p < 0.0001). There was no significant reduction in the incidence of oesophageal, gastric, thyroid, kidney, prostate cancer or multiple myeloma after bariatric surgery as compared to patients with morbid obesity who did not have bariatric surgery. Obesity-associated carcinogenesis is closely related to metabolic syndrome; visceral adipose dysfunction; aromatase activity and detrimental cytokine, adipokine and exosomal miRNA release. Bariatric surgery results in long-term weight loss in morbidly obese patients and improves metabolic syndrome. Bariatric surgery may decrease future overall cancer incidence and mortality, including the incidence of seven obesity-related cancers.

The Protective Effect of Bariatric Surgery on the Development of Colorectal Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Obesity is a known risk factor for developing colorectal cancer (CRC) and is associated with the formation of precancerous colonic adenomas. Bariatric surgery (BRS) is considered to reduce the cancer risk in morbidly obese patients. However, the currently available literature yields contradicting results regarding the impact of bariatric surgery on the incidence of CRC.

METHODS

A systematic literature search of the Medline, Embase, CENTRAL, CINAHL, Web of Science, and clinicaltrials.gov databases was undertaken following the PRISMA guidelines. A random effects model was selected.

RESULTS

Twelve retrospective cohort studies, incorporating a total of 6,279,722 patients, were eligible for inclusion in the final quantitative analysis. Eight studies originated from North America, while four reported on European patients. Patients in the Bariatric Surgery group exhibited a significantly reduced risk for developing colorectal cancer (RR 0.56, 95% CI 0.4-0.8, p < 0.001), while sleeve gastrectomy was found to be significantly associated with a smaller incidence of CRC (RR 0.55, 95% CI 0.36-0.83, p < 0.001), and gastric bypass and banding did not.

CONCLUSIONS

A significant protective effect of BRS against the development of CRC is implied. In the present analysis, the incidence rate of colorectal cancer was approximately halved amongst the obese individuals that were operated on.

Design of the Building Research in CRC prevention (BRIDGE-CRC) trial: a 6-month, parallel group Mediterranean diet and weight loss randomized controlled lifestyle intervention targeting the bile acid-gut microbiome axis to reduce colorectal cancer risk among African American/Black adults with obesity

BACKGROUND

Among all racial/ethnic groups, people who identify as African American/Blacks have the second highest colorectal cancer (CRC) incidence in the USA. This disparity may exist because African American/Blacks, compared to other racial/ethnic groups, have a higher prevalence of risk factors for CRC, including obesity, low fiber consumption, and higher intakes of fat and animal protein. One unexplored, underlying mechanism of this relationship is the bile acid-gut microbiome axis. High saturated fat, low fiber diets, and obesity lead to increases in tumor promoting secondary bile acids. Diets high in fiber, such as a Mediterranean diet, and intentional weight loss may reduce CRC risk by modulating the bile acid-gut microbiome axis. The purpose of this study is to test the impact of a Mediterranean diet alone, weight loss alone, or both, compared to typical diet controls on the bile acid-gut microbiome axis and CRC risk factors among African American/Blacks with obesity. Because weight loss or a Mediterranean diet alone can reduce CRC risk, we hypothesize that weight loss plus a Mediterranean diet will reduce CRC risk the most.

METHODS

This randomized controlled lifestyle intervention will randomize 192 African American/Blacks with obesity, aged 45-75 years to one of four arms: Mediterranean diet, weight loss, weight loss plus Mediterranean diet, or typical diet controls, for 6 months (48 per arm). Data will be collected at baseline, mid-study, and study end. Primary outcomes include total circulating and fecal bile acids, taurine-conjugated bile acids, and deoxycholic acid. Secondary outcomes include body weight, body composition, dietary change, physical activity, metabolic risk, circulating cytokines, gut microbial community structure and composition, fecal short-chain fatty acids, and expression levels of genes from exfoliated intestinal cells linked to carcinogenesis.

DISCUSSION

This study will be the first randomized controlled trial to examine the effects of a Mediterranean diet, weight loss, or both on bile acid metabolism, the gut microbiome, and intestinal epithelial genes associated with carcinogenesis. This approach to CRC risk reduction may be especially important among African American/Blacks given their higher risk factor profile and increased CRC incidence.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04753359 . Registered on 15 February 2021.

What is currently known about the association between bariatric surgery and cancer

BACKGROUND

Obesity increases the risk of multiple cancers.

OBJECTIVE

The purpose of this manuscript is to review the high-quality studies that have provided the most compelling evidence around the association between bariatric surgery and cancer risk.

SETTING

Literature review.

METHODS

The literature was reviewed for large high quality observational studies with well matched controls. Identified studies were summarized in this review.

RESULTS

Four large cohort studies were identified and summarized including the Swedish Obese Subjects study, the Utah cohorts, the Kaiser Permanente studies and the SPLENDID study. All four cohorts demonstrated a strong association between bariatric surgery and a reduction in cancer risk. Two of the cohorts showed a reduction in cancer related mortality, and two of the cohorts found a dose-response between amount of weight loss following bariatric surgery and cancer risk.

CONCLUSIONS

The evidence that bariatric surgery is associated with a reduced risk of cancer is compelling.

The impact of bariatric surgery on colorectal cancer risk

Obesity is considered a risk factor for different types of cancer, including colorectal cancer (CRC). Bariatric surgery has been associated with improvements in obesity-related co-morbidities and reductions in overall cancer risk. However, given the contradictory outcomes of several cohort studies, the impact of bariatric surgery on CRC risk appears controversial. Furthermore, measurement of CRC biomarkers following Roux-en-Y gastric bypass (RYGB) has revealed hyperproliferation and increased pro-inflammatory gene expression in the rectal mucosa. The proposed mechanisms leading to increased CRC risk are alterations of the gut microbiota and exposure of the colorectum to high concentrations of bile acids, both of which are caused by RYGB-induced anatomical rearrangements. Studies in animals and humans have highlighted the similarities between RYGB-induced microbial profiles and the gut microbiota documented in CRC. Microbial alterations common to post-RYGB cases and CRC include the enrichment of pro-inflammatory microbes and reduction in butyrate-producing bacteria. Lower concentrations of butyrate following RYGB may also contribute to an increased risk of CRC, given the anti-inflammatory and anticarcinogenic properties of this molecule. Laparoscopic sleeve gastrectomy appears to have a more moderate impact than RYGB; however, relatively few animal and human studies have investigated its effects on CRC risk. Moreover, evidence regarding the impact of anastomosis gastric bypass on one is even more limited. Therefore, further studies are required to establish whether the potential increase in CRC risk is restricted to RYGB or may also be associated with other bariatric procedures.

Does Bariatric Surgery Reduce the Risk of Colorectal Cancer in Individuals with Morbid Obesity? A Systematic Review and Meta-Analysis

Bariatric surgery has shown to be effective in producing sustained weight loss and the resolution of obesity related medical problems. Recent research focused on the role of obesity and adipose tissue in tumorigenesis, finding a strong crosslink through different mechanisms and highlighting an increase in cancer incidence in individuals with obesity. The aim of this meta-analysis is to find if bariatric surgery reduces the incidence of colorectal cancer in patients with obesity. We performed a meta-analysis including 18 studies (PROSPERO ID: CRD4202235931). Bariatric surgery was found to be significantly protective toward colorectal cancer incidence in individuals with obesity (HR: 0.81, p = 0.0142). The protective effect persisted when considering women (RR: 0.54, p = 0.0014) and men (RR: 0.74, p = 0.2798) separately, although this was not significant for the latter. No difference was found when comparing Roux-en-Y gastric bypass and sleeve gastrectomy. Bariatric surgery reduces the incidence of colorectal cancer in individuals with obesity independently from gender and surgical procedure. Prospective large cohort studies are needed to confirm these findings.

The implication of gut microbiota in recovery from gastrointestinal surgery

Recovery from gastrointestinal (GI) surgery is often interrupted by the unpredictable occurrence of postoperative complications, including infections, anastomotic leak, GI dysmotility, malabsorption, cancer development, and cancer recurrence, in which the implication of gut microbiota is beginning to emerge. Gut microbiota can be imbalanced before surgery due to the underlying disease and its treatment. The immediate preparations for GI surgery, including fasting, mechanical bowel cleaning, and antibiotic intervention, disrupt gut microbiota. Surgical removal of GI segments also perturbs gut microbiota due to GI tract reconstruction and epithelial barrier destruction. In return, the altered gut microbiota contributes to the occurrence of postoperative complications. Therefore, understanding how to balance the gut microbiota during the perioperative period is important for surgeons. We aim to overview the current knowledge to investigate the role of gut microbiota in recovery from GI surgery, focusing on the crosstalk between gut microbiota and host in the pathogenesis of postoperative complications. A comprehensive understanding of the postoperative response of the GI tract to the altered gut microbiota provides valuable cues for surgeons to preserve the beneficial functions and suppress the adverse effects of gut microbiota, which will help to enhance recovery from GI surgery.

Risk of non-hormonal cancer after bariatric surgery: meta-analysis of retrospective observational studies

BACKGROUND

Obesity is associated with an increased incidence of at least 13 types of cancer. Although bariatric surgery has been associated with a reduced risk of hormonal cancers, data for non-hormonal cancers are scarce. The aim of this study was to evaluate the effect of bariatric surgery on the incidence of non-hormonal cancers.

METHODS

Cochrane, Embase, PubMed, Scopus, and Web of Science were searched for articles between 1984 and 2018, following the PRISMA system. Meta-analysis was conducted using a random-effect model with subgroup analysis by procedure and cancer type.

RESULTS

From 2526 studies screened, 15 were included. There were a total of 18 583 477 patients, 947 787 in the bariatric group and 17 635 690 in the control group. In comparison to the non-surgical group, the bariatric group had a lower incidence of cancer (OR .65 (95 per cent c.i. 0.53 to 0.80); P < 0.002). In the subgroup analysis, Roux-en-Y gastric bypass and sleeve gastrectomy were associated with decreased risk of developing cancer, while no difference was observed with adjustable gastric banding. When evaluated by cancer type, liver (OR 0.417 (95 per cent c.i. 0.323 to 0.538)), colorectal (OR 0.64 (95 per cent c.i. 0.49 to 0.84)), kidney and urinary tract cancer (OR 0.77 (95 per cent c.i. 0.72 to 0.83)), oesophageal (OR 0.60 (95 per cent c.i. 0.43 to 0.85)), and lung cancer (OR 0.796 (95 per cent c.i. 0.45 to 0.80)) also presented a lower cancer incidence in the bariatric group.

CONCLUSION

Bariatric surgery is related to an almost 50 per cent reduction in the risk of non-hormonal cancers.

Alterations in Fecal Short-Chain Fatty Acids after Bariatric Surgery: Relationship with Dietary Intake and Weight Loss

Bariatric surgery is associated with weight loss attributed to reduced caloric intake, mechanical changes, and alterations in gut hormones. However, some studies have suggested a heightened incidence of colorectal cancer (CRC) has been associated with bariatric surgery, emphasizing the importance of identifying mechanisms of risk. The objective of this study was to determine if bariatric surgery is associated with decreases in fecal short-chain fatty acids (SCFA), a group of bacterial metabolites of fiber. Fecal samples (n = 22) were collected pre- (~6 weeks) and post-bariatric surgery (~4 months) in patients undergoing Roux-en-Y gastric bypass and sleeve gastrectomy. SCFA levels were quantified using liquid chromatography/mass spectrometry. Dietary intake was quantified using 24-h dietary recalls. Using an aggregate variable, straight SCFAs significantly decreased by 27% from pre- to post-surgery, specifically acetate, propionate, butyrate, and valerate. Pre-surgery weight was inversely associated with butyrate, with no association remaining post-surgery. Multiple food groups were positively (sugars, milk, and red and orange vegetables) and inversely (animal protein) associated with SCFA levels. Our results suggest a potential mechanism linking dietary intake and SCFA levels with CRC risk post-bariatric surgery with implications for interventions to increase SCFA levels.

The impact of bariatric and metabolic surgery on cancer development

Obesity (BMI ≥ 30 kg/m²) with related comorbidities such as type 2 diabetes mellitus, cardiovascular disease, sleep apnea syndrome, and fatty liver disease is one of the most common preventable risk factors for cancer development worldwide. They are responsible for at least 40% of all newly diagnosed cancers, including colon, ovarian, uterine, breast, pancreatic, and esophageal cancer. Although various efforts are being made to reduce the incidence of obesity, its prevalence continues to spread in the Western world. Weight loss therapies such as lifestyle change, diets, drug therapies (GLP-1-receptor agonists) as well as bariatric and metabolic surgery are associated with an overall risk reduction of cancer. Therefore, these strategies should always be essential in therapeutical concepts in obese patients. This review discusses pre- and post-interventional aspects of bariatric and metabolic surgery and its potential benefit on cancer development in obese patients.

Colorectal Cancer Risk Is Impacted by Sex and Type of Surgery After Bariatric Surgery

PURPOSE

Sex differences exist in the associations between obesity and the risk of colorectal cancer (CRC). However, limited data exist on how sex affects CRC risk after bariatric surgery.

MATERIALS AND METHODS

This retrospective cohort study used the 2012-2020 MarketScan database. We employed a propensity-score-matched analysis and precise coding to define CRC in this nationwide US study. Adjusted hazards ratio (HR) assessed CRC risk ≥ 6 months. In a restricted analysis, logistic regression with adjusted odds ratios (OR) examined CRC risk ≥ 3 years.

RESULTS

Our sample included 327,734 controls with severe obesity and 88,630 patients with Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (VSG). The odds of cessation of diabetes mellitus medications, a surrogate for diabetes remission, were higher post-surgery vs. controls, especially in RYGB and males. In females, CRC risk decreased post-RYGB compared to controls (HR = 0.40, 95%CI: 0.18-0.87, p = 0.02). However, VSG was not associated with lower CRC risk in females. Paradoxically, in males compared to controls, CRC risk trended toward an almost significant increase, especially after 3 years or more from surgery (OR = 2.18, 95%CI: 0.97-4.89, p = 0.06). Males had a higher risk of CRC, particularly rectosigmoid cancer, than females after bariatric surgery (HR = 2.69, 95% CI: 1.35-5.38, p < 0.001). Furthermore, diabetes remission was not associated with a lower CRC risk post-surgery.

CONCLUSION

Our data suggest an increased risk of CRC in males compared to females after bariatric surgery. Compared to controls, there was a decrease in CRC risk in females' post-RYGB but not VSG. Mechanistic studies are needed to explain these differences.

Jejunal adenocarcinoma after biliopancreatic diversion. Report of a case

The effects of bariatric surgery on the development of gastrointestinal cancers remain ill defined. We present a case of jejunal adenocarcinoma developing 19 years after biliopancreatic diversion (BPD) procedure according to Scopinaro's technique. The patient developed a marked distension of the biliopancreatic limb caused by a jejunal mass, evolving towards the so called "duodenal blowout". Emergency jejunal resection of the biliopancreatic limb, with creation of a new end-to-side jejunal-ileal anastomosis was necessary. The histological examination resulted in a moderately-differentiated ulcerated adenocarcinoma, with reactive lymph nodes and tumor-free resection margins. Tumors of the gastrointestinal system can arise following malabsorptive operations for morbid obesity, and they may be difficult to diagnose, since the symptoms are often attributed to the anatomical-functional changes resulting from this type of surgery. The case reported herein suggests that there is a need for surveillance in patients complaining of digestive symptoms after malabsorptive bariatric surgery.

Gut microbiota in bariatric surgery

Gut microbes share a symbiotic relationship with humans and perform several metabolic and physiological functions essential for human survival. It has been established in several scientific studies that obesity and other metabolic complications are always associated with disturbed gut microbiota profile, also called gut dysbiosis. In recent years, bariatric surgery has become a treatment of choice for weight loss, and it forms an important part of obesity management strategies across the globe. Interestingly, bariatric surgery has been shown to alter gut microbiota profile and synthesize short-chain fatty acids by gut microbes. In other words, gut microbes play a crucial role in better clinical outcomes associated with bariatric surgery. In addition, gut microbes are important in reducing weight and lowering the adverse events post-bariatric surgery. Therefore, several prebiotics, probiotics and postbiotics are recommended for patients who underwent bariatric surgery procedures for better clinical outcomes. The present review aims to understand the possible association between gut microbes and bariatric surgery and present scientific evidence showing the beneficial role of gut microbes in improving therapeutic outcomes of bariatric surgery.

Effect of bariatric surgery on cancer risk: results from an emulated target trial using population-based data

BACKGROUND

The impact of weight loss induced by bariatric surgery on cancer occurrence is controversial. To study the causal effect of bariatric surgery on cancer risk from an observational database, a target-trial emulation technique was used to mimic an RCT.

METHODS

Data on patients admitted between 2010 and 2019 with a diagnosis of obesity were extracted from a national hospital discharge database. Criteria for inclusion included eligibility criteria for bariatric surgery and the absence of cancer in the 2 years following inclusion. The intervention arms were bariatric surgery versus no surgery. Outcomes were the occurrence of any cancer and obesity-related cancer; cancers not related to obesity were used as negative controls.

RESULTS

A total of 1 140 347 patients eligible for bariatric surgery were included in the study. Some 288 604 patients (25.3 per cent) underwent bariatric surgery. A total of 48 411 cancers were identified, including 4483 in surgical patients and 43 928 among patients who did not receive bariatric surgery. Bariatric surgery was associated with a decrease in the risk of obesity-related cancer (hazard ratio (HR) 0.89, 95 per cent c.i. 0.83 to 0.95), whereas no significant effect of surgery was identified with regard to cancers not related to obesity (HR 0.96, 0.91 to 1.01).

CONCLUSION

When emulating a target trial from observational data, a reduction of 11 per cent in obesity-related cancer was found after bariatric surgery.

Roux-en-Y gastric bypass surgery in Zucker rats induces bacterial and systemic metabolic changes independent of caloric restriction-induced weight loss

Mechanisms of Roux-en-Y gastric bypass (RYGB) surgery are not fully understood. This study aimed to investigate weight loss-independent bacterial and metabolic changes, as well as the absorption of bacterial metabolites and bile acids through the hepatic portal system following RYGB surgery. Three groups of obese Zucker (fa/fa) rats were included: RYGB (n = 11), sham surgery and body weight matched with RYGB (Sham-BWM, n = 5), and sham surgery fed ad libitum (Sham-obese, n = 5). Urine and feces were collected at multiple time points, with portal vein and peripheral blood obtained at the end of the study. Metabolic phenotyping approaches and 16S rRNA gene sequencing were used to determine the biochemical and bacterial composition of the samples, respectively. RYGB surgery-induced distinct metabolic and bacterial disturbances, which were independent of weight loss through caloric restriction. RYGB resulted in lower absorption of phenylalanine and choline, and higher urinary concentrations of host-bacterial co-metabolites (e.g., phenylacetylglycine, indoxyl sulfate), together with higher fecal trimethylamine, suggesting enhanced bacterial aromatic amino acid and choline metabolism. Short chain fatty acids (SCFAs) were lower in feces and portal vein blood from RYGB group compared to Sham-BWM, accompanied with lower abundances of Lactobacillaceae, and Ruminococcaceae known to contain SCFA producers, indicating reduced bacterial fiber fermentation. Fecal γ-amino butyric acid (GABA) was found in higher concentrations in RYGB than that in Sham groups and could play a role in the metabolic benefits associated with RYGB surgery. While no significant difference in urinary BA excretion, RYGB lowered both portal vein and circulating BA compared to Sham groups. These findings provide a valuable resource for how dynamic, multi-systems changes impact on overall metabolic health, and may provide potential therapeutic targets for developing downstream non-surgical treatment for metabolic disease.

Clinical outcomes of bariatric surgery - Updated evidence

Obesity has grown to become a major health problem over the past few decades. Obesity-related comorbidities, such as diabetes mellitus, hypertension, obstructive sleep apnea, and dyslipidemia, are inextricably linked with increased adverse clinical consequences and mortality. Compared with other strategies for obesity, bariatric surgery is efficient in weight loss and has been proved to exert positive effects on obesity-related risk factors. This broad improvement in risk factors has resulted in substantial remission or reductions of comorbidities and better performance on clinical outcomes, including cardiovascular diseases, cancer, and mortality. With the development of surgical procedures, the safety of bariatric surgery has been validated and the rate of peri-operative death is low all over the world. Nonetheless, surgeons ought to be careful about potential complications, such as nutrition deficiencies, psychological disorders, or new digestive tract tumors after surgery. For patients with obesity, bariatric surgery might be a precious and crucial tool to bring additional benefits including comorbidities protection and life span extension. All patients with obesity should be engaged in a union consultation group to select a suitable treatment.

Association between bariatric surgery and risks of cancer among Chinese patients with type 2 diabetes mellitus: A retrospective cohort study

BACKGROUND

To examine risks of cancers, obesity-related cancers (eg, cancers in digestive organs, breast, ovary, kidney, thyroid, and myeloma), cancer-related mortality, and all-cause mortality in patients with type 2 diabetes mellitus (T2DM) and obesity who underwent bariatric surgery.

METHODS

A retrospective cohort of 1944 T2DM patients with obesity (345 bariatric surgery patients and 1599 matched controls) who were free of cancer from 2006 to 2017 was assembled. One-to-five propensity score matching followed by propensity score trimming was used to balance baseline covariates.

RESULTS

During a mean follow-up period of 37 months, there are risks that in 3.2%, 1.4%, 0.9%, and 3.2% of bariatric patients cancer, obesity-related cancer, cancer-related mortality, and all-cause mortality, respectively, would occur. Surgical patients were found to have reduced incidence rates (IRs) of obesity-related cancer (0.531/100 person-years, 95% confidence interval [CI]: 0.172-1.238/100 person-years) and cancer of breast and genital organs (0.394/100 person-years, 95% CI: 0.048-1.424/100 person-years) than matched control patients whose IRs for obesity-related cancer and cancer of breast and genital organs were 0.627/100 person-years (95% CI: 0.426-0.889/100 person-years) and 0.521/100 person-years (95% CI: 0.277-0.891/100 person-years), respectively. Patients in the surgical group had a significant reduction in risk of all-cause mortality (hazard ratio [HR] = 0.508, P = .041). Effects of bariatric surgery on any cancers (HR = 1.254, P = .510), obesity-related cancers (HR = 0.843, P = .724), and cancer mortality (HR = 1.304, P = .694) were not significant.

CONCLUSIONS

Bariatric surgery was not associated with risks of overall cancer, obesity-related cancer, and cancer mortality among T2DM patients with obesity at 3 years.

Spot-light on microbiota in obesity and cancer

Over the last few years, the complexity and diversity of gut microbiota within and across individuals has been detailed in relation to human health. Further, understanding of the bidirectional association between gut microbiota and metabolic disorders has highlighted a complimentary, yet crucial role for microbiota in the onset and progression of obesity-related cancers. While strategies for cancer prevention and cure are known to work efficiently when supported by healthy diet and lifestyle choices and physical activity, emerging evidence suggests that the complex interplay relating microbiota both to neoplastic and metabolic diseases could aid strategies for cancer treatment and outcomes. This review will explore the experimental and clinical grounds supporting the functional role of gut microbiota in the pathophysiology and progression of cancers in relation to obesity and its metabolic correlates. Therapeutic approaches aiding microbiota restoration in connection with cancer treatments will be discussed.

Colorectal cancer after bariatric surgery (Cric-Abs 2020): Sicob (Italian society of obesity surgery) endorsed national survey

BACKGROUND

The published colorectal cancer (CRC) outcomes after bariatric surgery (BS) are conflicting, with some anecdotal studies reporting increased risks. The present nationwide survey CRIC-ABS 2020 (Colo-Rectal Cancer Incidence-After Bariatric Surgery-2020), endorsed by the Italian Society of Obesity Surgery (SICOB), aims to report its incidence in Italy after BS, comparing the two commonest laparoscopic procedures-Sleeve Gastrectomy (SG) and Roux-en-Y gastric bypass (GBP).

METHODS

Two online questionnaires-first having 11 questions on SG/GBP frequency with a follow-up of 5-10 years, and the second containing 15 questions on CRC incidence and management, were administered to 53 referral bariatric, high volume centers. A standardized incidence ratio (SIR-a ratio of the observed number of cases to the expected number) with 95% confidence intervals (CI) was calculated along with CRC incidence risk computation for baseline characteristics.

RESULTS

Data for 20,571 patients from 34 (63%) centers between 2010 and 2015 were collected, of which 14,431 had SG (70%) and 6140 GBP (30%). 22 patients (0.10%, mean age = 53 ± 12 years, 13 males), SG: 12 and GBP: 10, developed CRC after 4.3 ± 2.3 years. Overall incidence was higher among males for both groups (SG: 0.15% vs 0.05%; GBP: 0.35% vs 0.09%) and the GBP cohort having slightly older patients. The right colon was most affected (n = 13) and SIR categorized/sex had fewer values < 1, except for GBP males (SIR = 1.07).

CONCLUSION

Low CRC incidence after BS at 10 years (0.10%), and no difference between procedures was seen, suggesting that BS does not trigger the neoplasm development.

Incidence of Colorectal Adenomas After Bariatric Surgery: Pre-operative Super Morbid Obesity Is Independently Associated with Increased Risk

PURPOSE

The impact of pre-bariatric surgery BMI on the incidence of colorectal adenomas in the post-operative period is unknown. Here we aim to evaluate the incidence of colorectal adenomas after bariatric surgery and to assess super morbid obesity (SMO) as a risk factor for post-operative colorectal adenomas.

MATERIALS AND METHODS

An inception cohort of 1639 patients that underwent bariatric surgery between 2011 and 2019 in a referral center was retrospectively analyzed. SMO was defined as BMI > 50.0 kg/m². Cox regression analysis was performed to assess the influence of pre-operative BMI on the primary outcome.

RESULTS

A total 381 patients (23.2% of the cohort) underwent colonoscopy and included in the analysis. Mean age was 51.1 years (± 10.6) with mean BMI of 42.2 kg/m² (± 6.2), and 49 patients (12.9%) had SMO. Median time to colonoscopy was 3.5 years. One hundred nine patients (28.6%) had colorectal polyps, and 38/109 (34.8%) had advanced adenoma. Two patients had colorectal cancer (CRC). Pre-procedural SMO was associated with diagnosis of colorectal polyp (HR 2.4, 95% CI 1.5-3.9, p < 0.001) and advanced adenomas (HR 4.2, 95% CI 2.0-8.9, p < 0.001) upon adjustment to previously reported risk factors of CRC.

CONCLUSION

Pre-procedural SMO is associated with increased risk of colorectal adenomas after bariatric surgery compared to obese and morbidly obese individuals. Pre-operative BMI should be incorporated into post-operative screening plan in this population.

Bariatric Surgery Reduces Cancer Risk in Adults With Nonalcoholic Fatty Liver Disease and Severe Obesity

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and increased risk of cancer. The impacts of bariatric surgery on cancer risk in NAFLD patients are unknown. We investigated the effect of bariatric surgery on cancer risk in patients with NAFLD and severe obesity using the MarketScan database.

METHODS

We conducted a retrospective cohort study of 18 to 64 years old newly diagnosed NAFLD patients with severe obesity between 2007 and 2017. We used Cox proportional hazard models to examine the association between bariatric surgery, modeled as a time-varying covariate, and the risks of any cancer and obesity-related cancer, while accounting for confounding using inverse probability of treatment weighting (IPTW).

RESULTS

A total of 98,090 patients were included in the study, 33,435 (34.1%) received bariatric surgery. In those without surgery, 1898 incident cases of cancer occurred over 115,890.11 person-years of follow-up, compared with 925 cancer cases over 67,389.82 person-years among surgery patients (crude rate ratio, 0.84; 95% CI, 0.77- 0.91). The IPTW-adjusted risk of any cancer and obesity-related cancer was reduced by 18% (hazard ratio, 0.82; 95% CI, 0.76-0.89) and 25% (hazard ratio, 0.65; 95% CI, 0.56-0.75), respectively, in patients with versus without bariatric surgery. The adjusted risks of any cancer and obesity-related cancer were significantly lower in cirrhotic versus non-cirrhotic patients who underwent surgery. In cancer-specific models, bariatric surgery was associated with significant risk reductions for colorectal, pancreatic, endometrial, thyroid cancers, hepatocellular carcinoma, and multiple myeloma.

CONCLUSION

Bariatric surgery was associated with significant reductions in the risks of any cancer and obesity-related cancer in NAFLD patients with severe obesity.

Incidence of polyp formation following bariatric surgery

BACKGROUND

Multiple studies have linked obesity to an increased risk of cancer. The correlation is so strong that the national cancer prevention guidelines recommend weight loss for patients with obesity to reduce their risk of cancer. Bariatric surgery has been shown to be very effective in sustained weight loss. However, there have been mixed findings about bariatric surgery and its effects on the risk of colorectal cancer.

OBJECTIVE

This study sought to examine bariatric surgery patients and their risk of pre-cancerous or cancerous polyps to elucidate any risk factors or associations between bariatric surgery and colorectal cancer.

SETTING

A retrospective review of the academic medical center's bariatric surgery database was performed from January 2010 to January 2017. Patients who underwent medical or surgical weight loss and had a subsequent colonoscopy were included in the study. Positive colonoscopy findings were described as malignant or premalignant polyps.

METHODS

A total of 1777 patients were included, with 1360 in the medical group and 417 in the surgical group. Data analysis included patient demographics, co-morbidities, procedure performed, surgical approach, weight loss, and colonoscopy findings. A multivariate analysis was used to determine whether an association exists between weight loss and incidence of colorectal polyps, and if so, whether the association different for medical versus surgical weight loss.

RESULTS

A higher percentage of body mass index (BMI) reduction was seen in the surgical group. An overall comparison showed average reductions in BMI of 27.7% in the surgical group and 3.5% in the medical group (P < .0001). Patients with the greatest reduction in BMI, regardless of medical or surgical therapy, showed a lower incidence of precancerous and cancerous polyps (P = .041).

CONCLUSION

This study offers a unique approach in examining the incidence of colorectal polyps related to obesity. Patients with the greatest reduction in their BMI, more common in the surgical group, had a lower incidence of precancerous and cancerous polyps.

Roux-en-Y gastric bypass-induced bacterial perturbation contributes to altered host-bacterial co-metabolic phenotype

BACKGROUND

Bariatric surgery, used to achieve effective weight loss in individuals with severe obesity, modifies the gut microbiota and systemic metabolism in both humans and animal models. The aim of the current study was to understand better the metabolic functions of the altered gut microbiome by conducting deep phenotyping of bariatric surgery patients and bacterial culturing to investigate causality of the metabolic observations.

METHODS

Three bariatric cohorts (n = 84, n = 14 and n = 9) with patients who had undergone Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG) or laparoscopic gastric banding (LGB), respectively, were enrolled. Metabolic and 16S rRNA bacterial profiles were compared between pre- and post-surgery. Faeces from RYGB patients and bacterial isolates were cultured to experimentally associate the observed metabolic changes in biofluids with the altered gut microbiome.

RESULTS

Compared to SG and LGB, RYGB induced the greatest weight loss and most profound metabolic and bacterial changes. RYGB patients showed increased aromatic amino acids-based host-bacterial co-metabolism, resulting in increased urinary excretion of 4-hydroxyphenylacetate, phenylacetylglutamine, 4-cresyl sulphate and indoxyl sulphate, and increased faecal excretion of tyramine and phenylacetate. Bacterial degradation of choline was increased as evidenced by altered urinary trimethylamine-N-oxide and dimethylamine excretion and faecal concentrations of dimethylamine. RYGB patients' bacteria had a greater capacity to produce tyramine from tyrosine, phenylalanine to phenylacetate and tryptophan to indole and tryptamine, compared to the microbiota from non-surgery, normal weight individuals. 3-Hydroxydicarboxylic acid metabolism and urinary excretion of primary bile acids, serum BCAAs and dimethyl sulfone were also perturbed following bariatric surgery.

CONCLUSION

Altered bacterial composition and metabolism contribute to metabolic observations in biofluids of patients following RYGB surgery. The impact of these changes on the functional clinical outcomes requires further investigation. Video abstract.

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, Cancer, and Risk Reduction with Bariatric Surgery

The prevalence of noncommunicable diseases has increased dramatically in North America and throughout the world and is expected to continue increasing in coming years. Obesity has been linked to several types of cancers and is associated with increased morbidity and mortality following cancer diagnosis. Bariatric surgery has emerged as the prominent model to evaluate the effects of intentional weight loss on cancer incidence and outcomes. Current literature, comprising prospective cohort investigations, indicates site-specific reductions in cancer risk with select bariatric procedures. Future research is required to establish evidence-based indications for bariatric surgery in the context of cancer prevention.

Colorectal Cancer Risk Following Bariatric Surgery in a Nationwide Study of French Individuals With Obesity

Importance

Although bariatric surgery is effective against morbid obesity, the association of this surgery with the risk of colorectal cancer remains controversial.

Objective

To assess whether bariatric surgery is associated with altered risk of colorectal cancer among individuals with obesity.

Design, Setting, and Participants

This retrospective, population-based, multicenter, cohort study based on French electronic health data included 1 045 348 individuals with obesity, aged 50 to 75 years, and free of colorectal cancer at baseline. All inpatients with obesity having data recorded during a hospital stay between 2009 and 2018 by the French national health insurance information system database were followed up for a mean (SD) of 5.3 (2.1) years for those who did not undergo bariatric surgery and 5.7 (2.2) years for those who underwent bariatric surgery. Two groups of patients comparable in terms of age, sex, body mass index, follow-up, comorbidities, and conditions who did or did not undergo surgery were also obtained by propensity score matching.

Exposures

Bariatric surgery (n = 74 131), including adjustable gastric banding, sleeve gastrectomy, gastric bypass; or no bariatric surgery (n = 971 217).

Main Outcomes and Measures

Primary outcome was incident colorectal cancer. Standardized incidence ratios were calculated using age-, sex-, and calendar year-matched colorectal cancer incidence among the general French population during the corresponding years. Secondary outcome was incident colorectal benign polyps.

Results

Among a total of 1 045 348 patients, the mean (SD) age was 57.3 (5.5) years for the 74 131 patients in the surgical cohort vs 63.4 (7.0) years for the 971 217 patients in the nonsurgical cohort. The mean (SD) follow-up was 6.2 (2.1) years for patients who underwent adjustable gastric banding, 5.5 (2.1) years for patients who underwent sleeve gastrectomy, and 5.7 (2.2) years for patients who underwent gastric bypass. In total, 13 052 incident colorectal cancers (1.2%) and 63 649 colorectal benign polyps were diagnosed. The rate of colorectal cancer was 0.6% in the bariatric surgery cohort and 1.3% in the cohort without bariatric surgery. In the latter cohort, 9417 cases were expected vs 12 629 observed, a standardized incidence ratio of 1.34 (95% CI, 1.32-1.36). In the bariatric surgery cohort, 428 cases were expected and 423 observed, a standardized incidence ratio of 1.0 (95% CI, 0.90-1.09). Propensity score-matched hazard ratios in comparable operated vs nonoperated groups were 0.68 (95% CI, 0.60-0.77) for colorectal cancer and 0.56 (95% CI, 0.53-0.59) for colorectal benign polyp. There were fewer new diagnoses of colorectal cancer after gastric bypass (123 of 22 343 [0.5%]) and sleeve gastrectomy (185 of 35 328 [0.5%]) than after adjustable gastric banding (115 of 16 460 [0.7%]), and more colorectal benign polyps after adjustable gastric banding (775 of 15 647 [5.0%]) than after gastric bypass (639 of 20 863 [3.1%]) or sleeve gastrectomy (1005 of 32 680 [3.1%]).

Conclusion and Relevance

The results of this nationwide cohort study suggested that following bariatric surgery, patients with obesity share the same risk of colorectal cancer as the general population, whereas for patients with obesity who do not undergo bariatric surgery, the risk is 34% above that of the general population.

Gastrointestinal manifestations after Roux-en-Y gastric bypass surgery in individuals with and without type 2 diabetes

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery is an effective treatment for obesity, which improves cardiovascular health and reduces the risk of premature mortality. However, some reports have suggested that RYGB may predispose patients to adverse health outcomes, such as inflammatory bowel disease (IBD) and colorectal cancer.

OBJECTIVES

The present prospective study aimed to evaluate the impact of RYGB surgery on cardiovascular risk factors and gastrointestinal inflammation in individuals with and without type 2 diabetes (T2D).

SETTING

University hospital setting in Finland.

METHODS

Blood and fecal samples were collected at baseline and 6 months after surgery from 30 individuals, of which 16 had T2D and 14 were nondiabetics. There were also single study visits for 6 healthy reference patients. Changes in cardiovascular risk factors, serum cholesterol, and triglycerides were investigated before and after surgery. Fecal samples were analyzed for calprotectin, anti-Saccharomyces cerevisiae immunoglobulin A antibodies (ASCA), active lipopolysaccharide (LPS) concentration, short-chain fatty acids (SCFAs), intestinal alkaline phosphatase activity, and methylglyoxal-hydro-imidazolone (MG-H1) protein adducts formation.

RESULTS

After RYGB, weight decreased on average -21.6% (-27.2 ± 7.8 kg), excess weight loss averaged 51%, and there were improvements in cardiovascular risk factors. Fecal calprotectin levels (P < .001), active LPS concentration (P < .002), ASCA (P < .02), and MG-H1 (P < .02) values increased significantly, whereas fecal SCFAs, especially acetate (P < .002) and butyrate (P < .03) levels, were significantly lowered.

CONCLUSION

The intestinal homeostasis is altered after RYGB, with several fecal markers suggesting increased inflammation; however, clinical significance of the detected changes is currently uncertain. As chronic inflammation may predispose patients to adverse health effects, our findings may have relevance for the suggested association between RYGB and increased risks of incident IBD and colorectal cancer.

Malignancy in bariatric surgery patients: a French multisite cohort

BACKGROUND

Bariatric surgery is associated with decreased cancer-related mortality. An indefinite proportion of patients that undergo bariatric surgery have a history of malignancy or will develop cancer. In these patients, weight loss and oncologic evolution needed to be assessed. The aim of this study was to report the results of patients diagnosed with malignancy before and after bariatric surgery in a French multisite cohort.

METHODS

We conducted a retrospective cohort study of all patients who underwent bariatric surgery in six university centers. Patients were divided in two groups: patients with a preoperative history of malignancy and patients diagnosed with malignancy during the follow-up. Both groups were compared with control groups of patients that underwent surgery during the same period.

RESULTS

From 2008 to 2018, 8927 patients underwent bariatric surgery. In patients with a history of malignancy (n = 90), breast and gynecologic cancers were predominant (37.8%). Median interval between malignancy and surgery was 60 (38-118) months. After a follow-up of 24 (4-52) months, 4 patients presented with cancer recurrence. Comparative analysis demonstrated equivalent weight loss one year after surgery. In patients with postoperative malignancy (n = 32), breast and gynecologic cancers were also predominant (40.6%). Median interval between surgery and malignancy was 22 (6-109) months. In the comparative analysis, weight loss was similar at 2 years.

CONCLUSIONS

History of malignancy should not be considered as an absolute contraindication for bariatric surgery. Gynecological cancer screening should be reinforced before and after surgery. The development of malignancy postoperatively does not seem to affect mid-term bariatric outcomes.

Bariatric surgery decreases the number of first-time hospital admissions for cancer in severely obese patients. A retrospective analysis of the National Inpatient Sample database

BACKGROUND

According to the U.S. Centers for Disease Control, cancers linked to overweight or obesity accounted for roughly 40% of all U.S. malignancies in 2014.

OBJECTIVES

The primary aim of this epidemiologic study was to assess whether bariatric surgery might have any preventative role against obesity-linked cancers among individuals with obesity.

SETTING

Hospitals across the United States participating in the National Inpatient Sample database, created, updated, and monitored by the U.S. Healthcare Cost and Utilization Project.

METHODS

National Inpatient Sample data collected from 2010 to 2014 were examined to identify any difference in the number of first cancer-related hospitalizations, as a proxy for cancer incidence, between patients with a history of prior bariatric surgery (cases) and those without (controls). Patients with any prior cancer diagnosis were excluded. To match the body mass index ≥35 kg/m² generally required for bariatric surgery, all controls had to have a body mass index ≥35 kg/m². International Classification of Diseases-9 codes were employed to identify admissions for 13 obesity-linked cancers. Multivariate logistic regression analysis was performed to identify any case-control differences, after matching for all baseline demographic, co-morbidity, and cancer risk-factor variables. All percentages and means (with confidence intervals) were weighted, per Healthcare Cost and Utilization Project guidelines.

RESULTS

Among 1,590,579 controls and 247,015 bariatric surgery cases, there were 29,822 (1.93%; 95% confidence interval 1.91-1.96) and 3540 (1.43%; 1.38-1.47) first hospitalizations for cancer (adjusted odds ratio 1.17; 1.13-1.23; P < .0001).

CONCLUSIONS

Preliminary findings from a large U.S. database suggest that bariatric surgery may reduce the incidence of cancer in patients considered at high risk because of severe obesity.