Can Bariatric Surgery Prevent Colorectal Cancer?

Recently, findings from a population-based study revealed a possible association between bariatric surgery and reduced colorectal cancer incidence. The findings were first presented at Digestive Disease Week® (DDW) 2023 by Vibhu Chittajallu, MD and gastroenterology fellow at Case Western Reserve University and University Hospitals at Cleveland, OH.

According to Dr Chittajallu, their findings show that bariatric surgery reduced the risk of de novo cancer, or when cancer first occurs, by half. These findings were applicable particularly to obesity-related cancers including colorectal cancer, which also saw lower prevalence rates compared to the group that didn’t receive the surgery.

While the findings are initially promising, existing research suggests that the association between bariatric surgery and colorectal cancer has long been controversial. While some studies support the direct association between surgery and lower colorectal cancer incidence, other studies have found the opposite to be true.

What can we make from these recent findings, and what do we know about bariatric surgery and colorectal cancer?

Bariatric surgery is a collective term used to represent weight loss surgeries. These surgeries are usually characterized by an alteration of the digestive system to induce weight loss. They are sometimes recommended to obese or severely obese individuals who find difficulty losing weight through other means, such as diet or physical activity.

There are many different types of bariatric surgery, including the Roux-en-y bypass, biliopancreatic diversion with duodenal switch and sleeve gastrectomy. Each of these procedures comes with its associated risks and side effects, and patients who undergo surgery are also required to commit to a drastically different lifestyle post-surgery. This is to ensure that the procedure can effectively help with weight loss and also to prevent post-surgery complications.

Despite bariatric surgery and colorectal cancer still having an unclear association, let alone a clear cause-and-effect relationship, there are a few hypotheses as to how and why there may be an association in both decreasing and increasing colorectal cancer risk.

Bariatric surgery helps manage various colorectal cancer risks

In most cases, the purpose of bariatric surgery is to help the individual lose excess weight, particularly if there are other health concerns such as type 2 diabetes or sleep apnea that need to be managed. By shedding excess fat through weight loss, bariatric surgery inadvertently also lowers the risk of colorectal cancer, of which obesity is a well-documented risk factor.

In addition, dietary changes are often recommended to bariatric surgery patients, and dietary restrictions such as consuming less red meat and greasy, high-fat foods significantly reduce diet-related colorectal cancer risk. Furthermore, consuming alcohol and smoking tobacco are strongly advised against due to potential complications that can arise post-surgery.

In a sense, bariatric surgery may help reduce colorectal cancer risk through more than just managing obesity. How, then, do we explain the findings of bariatric surgery and higher colorectal cancer incidence?

Bariatric surgery affects digestive microbiota and secretion levels

Of the several cohort and biomarker studies that suggest bariatric surgery is associated with increased colorectal cancer risk, the alteration in gut microbiota and digestive fluid secretions have been the suspected cause of increased risk.

The health of the gut microbiota can be thought of as symbiotic with that of the colon — the prevalence of good bacteria benefits the gut, and a gut that is not exposed to carcinogens and toxins will also promote the growth of good bacteria. Particularly in instances of Roux-en-Y gastric bypass, microbial alterations that greatly resemble those observed in colorectal cancer patients were found, suggesting that the altered gut microbiota may be one pathway through which colorectal cancer develops. This is besides higher serum concentrations of bile acids and lower levels of butyrate, which too could contribute to elevated colorectal cancer risks. Nonetheless, both these potential causes require further research.

While it may not be reassuring to hear that the proverbial jury is still out on the true relationship between bariatric surgery and colorectal cancer, it is still important to be aware of the potential association. Bariatric surgery is often permanent and requires lifelong commitment to a new and changed diet and lifestyle.

If bariatric surgery has been recommended to you, you may like to consult with medical professionals on the pros and cons, especially if you have higher-than-average risk of developing colorectal cancer. Ensure to carefully evaluate all the associated risks to make an informed and confident decision. It may be a difficult decision, but listening to the advice of your doctors would be the best way to move forward.