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1st July 2022
Patient who have undergone bariatric surgery have a significantly lower risk of developing an obesity-related cancer as well as cancer-related mortality. This was the conclusion of a cohort study by a team of US researchers.
Individuals with a body mass index (BMI) above 25 are considered to be overweight but when the BMI exceeds 30, these individuals are deemed to be obese. Data from the World Health Organisation suggest that in 2016, 1.9 billion adults across the world were classed as overweight and 650 million obese. Although obesity increases the risk of cardiovascular disease, obesity has also been found to be associated with greater overall mortality in patients with cancer.
Whilst dieting helps many people to lose weight, one of the most effective weight loss strategies is surgery and in one follow-up study after a Roux-en-Y gastric bypass, the mean weight loss change from baseline was 35 kg at 12 years. Given the elevated risk of certain cancers in those who are obese, could weight loss reduce the risk of subsequently developing an obesity-related cancer? Unfortunately, the evidence base supporting this premise is limited apart from one study in patients who underwent bariatric surgery and which found that after a mean follow-up of 12.5 years, total cancer incidence was significantly lower in the surgical group compared to controls. Nevertheless, a limitation of the study was the absence of a matched control group, particularly in relation to possible cancer risk factors such as smoking history.
Consequently, there remains some uncertainty over whether weight loss can reduce the risk of cancer and this was the basis for the current study. The US team undertook the Surgical Procedures and Long-term Effectiveness in Neoplastic Disease Incidence and Death (SPLENDID) trial, which was a retrospective, observational, matched, cohort study in adults with obesity who either underwent bariatric surgery or who received usual care (i.e., no surgery). Participants were included if they had a BMI of between 35 and 80 and underwent either Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG). The primary endpoint of the study was the first occurrence of 1 of 13 types of obesity-associated cancers including oesophageal adenocarcinoma, renal cell carcinoma, colon, rectum, liver and pancreatic cancer. As a secondary endpoint, the team considered the incidence of all types of cancer and cancer-related mortality.
Bariatric surgery and cancer development
A total of 30,318 patients with a median age of 46 years (77% female) including 5,053 who underwent bariatric surgery, (RYGB 66%) were included in the analysis. After 10 years, participants in the bariatric surgery group had lost 27.5 kg compared to 2.7 kg in the control group (p <0.001).
During the period of follow-up, 96 patients in the bariatric surgery group and 780 in the control group developed one of the obesity-related cancers, giving an incidence rate of 3 vs 4.6 events (surgery vs control) per 1000 person-years.
The cumulative incidence of the primary endpoint at 10 years was 2.9% in the surgery group and 4.9% in the non-surgical (control group) and which was statistically significant (hazard ratio, HR = 0.68, 95% CI 0.53 – 0.87, p = 0.02). In addition, the cumulative incidence of cancer-related mortality at 10 years was 0.8% in the surgical group compared to 1.4% in the control group and which again, as statistically significant (HR = 0.52, 95% CI 0.31 – 0.88, p = 0.01).
Based on these findings, the authors concluded that bariatric surgery is associated with a significantly lower incidence of obesity-associated cancer and cancer-related mortality.
Aminian A et al. Association of Bariatric Surgery With Cancer Risk and Mortality in Adults With Obesity JAMA 2022