What Is Bariatric (Obesity) Surgery? How Does It Affect Cancer Development?

The World Health Organization (WHO) points out that obesity, which is growing rapidly in most developed and developing countries and threatens public health, is one of the most serious problems.

Obesity substantially increases the risk of cancers such as postmenopausal (after menopause) breast, endometrial (uterine), colon, liver, pancreatic and ovarian cancer (see the relationship between obesity and cancer).

According to previous studies, bariatric surgeries (obesity operations) are significantly associated with a reduction in the incidence of cancer overall and obesity-related cancers.

What Is Bariatric Surgery?

Gastric bypass and other weight-loss operations, collectively known as bariatric surgery, involve changes to the digestive system that help with weight loss.

Obesity surgery is performed when diet and exercise programs do not work or when you have a health problem because of your weight.

Some operations limit how much you can eat, while others work by reducing your body’s ability to absorb nutrients. There are also operations that achieve both aims.

These operations appear to be more effective in people with short- or long-standing obesity than continuous dietary programs for losing weight.

Bariatric surgery is a cost-effective way to manage obesity, reduce obesity-related cardiovascular risk and improve quality of life.

Although these operations generally have many benefits, most forms are major procedures that can pose serious risks and side effects. You must also make healthy dietary changes permanent and exercise regularly to help ensure long-term success after bariatric surgery.

How Does Bariatric Surgery Affect Tumor Development, Diagnosis and Treatment?

Retrospective studies show that bariatric surgery is significantly associated with a reduction in the incidence of cancer overall and obesity-related cancers.

Recent studies have shown that bariatric surgeries are significantly associated with a reduced risk of breast and uterine cancer, but are not associated with colorectal or pancreatic cancer risk.

Breast and endometrial (uterine) cancers are both highly sensitive to estrogen levels. Weight loss has previously been shown to reduce circulating estrogen levels. This also reduces the risk of these two cancer types.

The biomolecular mechanisms of obesity-associated endometrial cancer development include insulin-resistance pathways and exogenous estrogen formation. Because adipose tissue contains the aromatase enzyme, circulating estradiol levels are known to be affected by the amount of adipose tissue. In addition, through increased levels of C-reactive protein, TNF-α and interleukin-6, obesity causes a state of chronic inflammation that leads to insulin resistance. Insulin resistance is associated with low sex hormone-binding globulin, further increases estrogen bioavailability, and is associated with tumor formation and tumor metastasis.

In addition to inducing weight loss, bariatric surgery is thought to reduce cancer risk through multiple weight-loss-independent mechanisms. These include rearrangement of gastrointestinal anatomy, reduced inflammation and inflammatory markers, altered fat and bile metabolism, changes in gut hormone secretion, metabolic regulation, changes in intestinal microflora, and changes in intestinal gluconeogenesis.

While bariatric surgeries are associated with a reduction in hormone-related cancer risk, gastric bypass may increase colorectal cancer risk. In line with these results, there are also findings of increased rectal mucosal proliferation and biomarker levels after gastric bypass surgery, and that an inflammatory environment after bariatric surgery stimulates hyperproliferation of the intestinal mucosa.

A study evaluating the relationship between gastric bypass and cancer incidence or mortality also reported that gastric bypass was significantly associated with reduced cancer mortality, but not with reduced cancer incidence.

Conclusion

Bariatric surgery operations are increasing dramatically worldwide. As obesity increases, bariatric procedures are expected to rise steadily over the next 10 years.

Although bariatric surgery is a highly effective way to reduce the burden of obesity, it remains unclear how these operations and the resulting changes in body weight, metabolism and hormones affect tumor development, diagnosis and treatment. Recent studies indicate that bariatric surgery may reduce the incidence of certain cancer types, especially the hormone-related breast and uterine cancers, but the underlying reasons have not yet been understood. Conversely, certain bariatric methods may also predispose people to certain cancers or hinder their diagnosis. More studies are needed to predict the functional effects and side effects.