Bariatric Surgery and Cancer Risk

Delhi: Patients who have had bariatric surgery may be at a higher risk for colon cancer, a recent study in the International Journal of Cancer has suggested. Further, the support for an increased risk of rectal cancer was weaker.

Obesity is a risk factor for colorectal cancer (CRC). However, previous studies have found bariatric surgery to be associated with increased risk for CRC. Current evidence examining bariatric surgery and the risk of colorectal cancer is limited and inconsistent.

Wenjing Tao, Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Solna, Sweden, and colleagues determined whether the risk for colon and/or rectal cancer increases over time following bariatric surgery.

In the study, the researcher used data from the Nordic Obesity Surgery Cohort. Using the data they analyzed CRC risk after bariatric surgery in patients aged 18 or older with a recorded diagnosis of obesity. The study period lasted from January 1980 to December 2015. The two study outcomes were colon cancer and rectal cancer, which were identified from codes and corresponding variables in national cancer registers.

Standardized incidence ratios (SIR) and 95% CI were used to compare the incidence of colon cancer and rectal cancer in patients diagnosed with obesity who had and had not undergone bariatric surgery with the incidence in the corresponding background population. Multivariable Cox regression was used to compare the risk for colon cancer and rectal cancer in patients who had undergone bariatric surgery with that among obese patients who had not had surgery. Researchers used hazard ratios (HR) with 95% CI adjusted for confounders such as diabetes, smoking, heavy alcohol use, and inflammatory bowel disease.

Key Findings of the Study

• Among 502,772 cohort participants with an obesity diagnosis, 49,931 (9.9%) underwent bariatric surgery.
• The overall SIR of colon cancer was increased after bariatric surgery (SIR 1.56), with higher SIRs ≥10 years postsurgery.
• The overall HR of colon cancer in operated compared to nonoperated participants was 1.13 and 1.55, 10–14 years after bariatric surgery.
• Bariatric surgery did not significantly increase the risk of rectal cancer (SIR 1.14; HR 1.08), but the risk estimates increased with longer follow-up periods.

"Our study suggests that bariatric surgery is associated with an increased risk of colon cancer, while the support for an increased risk of rectal cancer was weaker," concluded the authors.

The study, "Colon and rectal cancer risk after bariatric surgery in a multicountry Nordic cohort study," is published in the International Journal of Cancer.

DOI: https://doi.org/10.1002/ijc.32770