Bariatric Surgery and Cancer Risk

Breast Cancer Risk After Bariatric Surgery and Influence of Insulin Levels: A Nonrandomized Controlled Trial

Importance

Obesity and insulin are risk factors for breast cancer, and retrospective studies suggest bariatric surgery reduces breast cancer risk in women. However, long-term prospective data on breast cancer risk after bariatric surgery and the role of baseline insulin levels are lacking.

Objective

To examine if bariatric surgery is associated with breast cancer incidence in women and if treatment benefit is modified by baseline insulin levels.

Design, Setting, and Participants

The Swedish Obese Subjects (SOS) study was a nonrandomized intervention trial designed to investigate the long-term effects of bariatric surgery on obesity-related mortality and morbidity. Study recruitment took place between 1987 and 2001, and median (IQR) follow-up time was 23.9 years (20.1-27.1) years. The study was conducted at 25 public surgical departments and 480 primary health care centers in Sweden and included 2867 women aged 37 to 60 years and with body mass index 38 or greater (calculated as weight in kilograms divided by height in meters squared).

Intervention

In the surgery group (n = 1420), 260 women underwent gastric banding, 970 vertical banded gastroplasty, and 190 gastric bypass. The remaining contemporaneously matched control individuals (n = 1447) received usual obesity care.

Main Outcome and Measures

Breast cancer, the main outcome of this secondary report, was not a predefined outcome in the SOS study. Breast cancer events were identified in the Swedish National Cancer Registry.

Results

The study population comprised 2867 women with a mean (SD) age of 48.0 (6.2) years. During follow-up, there were 154 breast cancer events, 66 in the surgery group and 88 in the usual care group, and a decreased risk of breast cancer was observed in the bariatric surgery group (hazard ratio [HR], 0.68; 95% CI, 0.49-0.94; P = .019; adjusted HR, 0.72; 95% CI, 0.52-1.01; P = .06). The surgical treatment benefit on breast cancer risk was greater in women with baseline insulin levels above the median 15.8 μIU/L (HR, 0.48; 95% CI, 0.31-0.74; P = .001; adjusted HR, 0.55; 95% CI, 0.35-0.86; P = .008) compared to those below (HR, 0.95; 95% CI, 0.59-1.53; P = .84; adjusted HR, 1.01; 95% CI, 0.61-1.66; P = .97; interaction P = .02).

Conclusions and Relevance

This prospective clinical trial indicated a reduced risk of breast cancer after bariatric surgery in women with obesity. The surgical treatment benefit was predominantly seen in women with hyperinsulinemia.

Trial Registration

ClinicalTrials.gov Identifier: NCT01479452.

Risk of Esophageal Adenocarcinoma After Bariatric Surgery: A Meta-Analysis of Retrospective Studies

PURPOSE

This study aims to systematically review and meta-analyze the evidence on the risk of esophageal adenocarcinoma (EAC) following metabolic and bariatric surgery (MBS).

MATERIALS AND METHODS

A systematic literature search was conducted on the China National Knowledge Infrastructure (CNKI), Wanfang, EMBASE, MEDLINE, Web of Science, The Cochrane Library, and PubMed databases. Meta-analysis utilized odds ratios (ORs) and 95% confidence intervals (CIs) to analyze the correlation between MBS and the risk of EAC. Meta-analysis was performed using STATA software (version 12.0).

RESULTS

Fourteen studies involving patients with obesity undergoing bariatric surgery and control groups receiving conventional treatment were included. The meta-analysis indicated a reduction in the overall incidence of esophageal cancer after bariatric surgery (OR = 0.69, 95% CI: 0.51-0.95, P = 0.022). Subgroup analysis results demonstrated a decreased risk of EAC in European patients with obesity undergoing MBS treatment (OR: 0.60, 95% CI: 0.38-0.95, P = 0.028). In studies with a sample size greater than or equal to 100,000 patients, the risk of EAC in patients with obesity undergoing MBS was significantly lower than the non-surgery group (OR: 0.59, 95% CI: 0.42-0.83, P = 0.003). Articles published before 2020 and those published in 2020 or earlier showed a significant difference in the incidence of EAC between the surgery and non-surgery groups (OR: 0.57, 95% CI: 0.43-0.75, P < 0.001). The risk of EAC in patients with obesity with a follow-up time of less than 5 years was statistically significant (OR: 0.46, 95% CI: 0.25-0.82, P = 0.009).

CONCLUSION

Our meta-analysis results suggest a reduced risk of esophageal cancer in patients with obesity after bariatric surgery.

PROSPERO REGISTRATION

CRD 42024505177.

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.

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.

The Effect of Bariatric Surgery upon Diabetes Mellitus: A Proof of Concept by Using the Case of the Mid-Term Effect of Lap Adjustable Gastric Banding (LAGB) on Patients with Diabetes

Obesity is a worldwide epidemic, with numbers on the rise in the world. Obesity is strongly correlated with increased morbidity and mortality. One of the major factors affecting this increase is comorbid diseases such as diabetes mellitus (DM), which is strongly associated with and dependent on the degree of obesity. Thus, it is not surprising that when efficient surgical treatments were found to battle obesity, researchers soon found them to be relevant and effective for battling DM as well. Laparoscopic Adjustable Gastric Banding (LAGB) is a common surgical treatment for morbid obesity. LAGB has the potential to improve control of the comorbidities of morbid obesity, primarily diabetes mellitus (DM). Our hypothesis was that patients treated with LAGB would have a long-term improvement in the control of DM and that due to its unique mechanism of action, this can lend us a better understanding of how to battle diabetes in an efficient and effective way. This was a cohort study based on patients who underwent LAGB surgery in our institution 4 to 7 years previously and had DM type 2 at the time of surgery. Data were collected from patient’s charts and a telephone interview-based questionnaire including demographics, health status, and quality-of-life assessment (Bariatric Analysis and Reporting Outcome System [BAROS]). Seventy patients participated in the current study. The average follow-up time was 5.1 ± 0.9 years post-surgery. The average weight prior to surgery was 122.0 ± 20.2 kg, and on the day of the interview it was 87.0 ± 17.6 kg (p < 0.001). The average body mass index before surgery was 43.8 ± 5.1, and on the day of the interview it was 31.2 ± 4.8 (p < 0.001). On the day of the interview, 47.1% of the participants were cured of DM (not receiving treatment, whether dietary or pharmacologic). The sum of ranks for diabetes was lower after the surgery (p < 0.001), as was HTN and its treatment (p < 0.001). We have shown in this study that LAGB is an effective treatment for morbid obesity, as well as two comorbidities that come with it—DM type 2 and Hypertension (HTN)—in a longer period than previously shown, and with a unique look at the underlying mechanism of action of this procedure. There is a need for further studies to consolidate our findings and characterize which patients are more prone to enjoy these remarkable surgical benefits.

The role of obesity and bariatric surgery-induced weight loss in breast cancer

Obesity is a complex metabolic condition considered a worldwide public health crisis, and a deeper mechanistic understanding of obesity-associated diseases is urgently needed. Obesity comorbidities include many associated cancers and are estimated to account for 20% of female cancer deaths in the USA. Breast cancer, in particular, is associated with obesity and is the focus of this review. The exact causal links between obesity and breast cancer remain unclear. Still, interactions have emerged between body mass index, tumor molecular subtype, genetic background, and environmental factors that strongly suggest obesity influences the risk and progression of certain breast cancers. Supportive preclinical research uses various diet-induced obesity models to demonstrate that weight loss, via dietary interventions or changes in energy expenditure, reduces the onset or progression of breast cancers. Ongoing and future studies are now aimed at elucidating the underpinning mechanisms behind weight-loss-driven observations to improve therapy and outcomes in patients with breast cancer and reduce risk. This review aims to summarize the rapidly emerging literature on obesity and weight loss strategies with a focused discussion of bariatric surgery in both clinical and preclinical studies detailing the complex interactions between metabolism, immune response, and immunotherapy in the setting of obesity and breast cancer.

Response to immune checkpoint blockade improved in pre-clinical model of breast cancer after bariatric surgery

Bariatric surgery is a sustainable weight loss approach, including vertical sleeve gastrectomy (VSG). Obesity exacerbates tumor growth, while diet-induced weight loss impairs progression. It remains unknown how bariatric surgery-induced weight loss impacts cancer progression or alters response to therapy. Using a pre-clinical model of obesity followed by VSG or diet-induced weight loss, breast cancer progression and immune checkpoint blockade therapy were investigated. Weight loss by VSG or weight-matched dietary intervention before tumor engraftment protected against obesity-exacerbated tumor progression. However, VSG was not as effective as diet in reducing tumor burden despite achieving similar weight and adiposity loss. Leptin did not associate with changes in tumor burden; however, circulating IL-6 was elevated in VSG mice. Uniquely, VSG tumors displayed elevated inflammation and immune checkpoint ligand PD-L1+ myeloid and non-immune cells. VSG tumors also had reduced T lymphocytes and markers of cytolysis, suggesting an ineffective anti-tumor microenvironment which prompted investigation of immune checkpoint blockade. While obese mice were resistant to immune checkpoint blockade, anti-PD-L1 potently impaired tumor progression after VSG through improved anti-tumor immunity. Thus, in formerly obese mice, surgical weight loss followed by immunotherapy reduced breast cancer burden. Finally, we compared transcriptomic changes in adipose tissue after bariatric surgery from patients and mouse models. A conserved bariatric surgery-associated weight loss signature (BSAS) was identified which significantly associated with decreased tumor volume. Findings demonstrate conserved impacts of obesity and bariatric surgery-induced weight loss pathways associated with breast cancer progression.

As the number of people classified as obese rises globally, so do obesity-related health risks. Studies show that people diagnosed with obesity have inflammation that contributes to tumor growth and their immune system is worse at detecting cancer cells. But weight loss is not currently used as a strategy for preventing or treating cancer.

Surgical procedures for weight loss, also known as ‘bariatric surgeries’, are becoming increasingly popular. Recent studies have shown that individuals who lose weight after these treatments have a reduced risk of developing tumors. But how bariatric surgery directly impacts cancer progression has not been well studied: does it slow tumor growth or boost the anti-tumor immune response?

To answer these questions, Sipe et al. compared breast tumor growth in groups of laboratory mice that were obese due to being fed a high fat diet. The first group of mice lost weight after undergoing a bariatric surgery in which part of their stomach was removed. The second lost the same amount of weight but after receiving a restricted diet, and the third underwent a fake surgery and did not lose any weight. The experiments found that surgical weight loss cuts breast cancer tumor growth in half compared with obese mice. But mice who lost the same amount of weight through dietary restrictions had even less tumor growth than surgically treated mice.

The surgically treated mice who lost weight had more inflammation than mice in the two other groups, and had increased amounts of proteins and cells that block the immune response to tumors. Giving the surgically treated mice a drug that enhances the immune system’s ability to detect and destroy cancer cells reduced inflammation and helped shrink the mice’s tumors. Finally, Sipe et al. identified 54 genes which were turned on or off after bariatric surgery in both mice and humans, 11 of which were linked with tumor size.

These findings provide crucial new information about how bariatric surgery can impact cancer progression. Future studies could potentially use the conserved genes identified by Sipe et al. to develop new ways to stimulate the anti-cancer benefits of weight loss without surgery.