Bariatric surgery was linked to fewer obesity-related cancers, at any adult age

Design

Population-based registry cohort (Nordic Obesity Surgery Cohort), 1992–2023

Population

784,105 adults aged 18–59 with obesity; 99,614 had bariatric surgery

Primary outcome

Incidence of obesity-related cancer

Effect

aIRR 0.81 (95% CI 0.77–0.85); liver 0.49, endometrial 0.51; pancreatic 2.21 (1.44–3.39) in younger adults

This Nordic registry cohort followed 784,105 adults aged 18 to 59 with recorded obesity in Denmark, Finland and Sweden between 1992 and 2023; 99,614 had bariatric surgery. The outcome was a set of obesity-related cancers, including breast, endometrial, ovarian, oesophageal adenocarcinoma, liver, pancreas, colorectal and kidney cancer and myeloma.

After adjustment, surgery was associated with about 19% fewer obesity-related cancers. The relative reduction was the same in people aged 18 to 39 and 40 to 59, and similar in men and women for the cancers both sexes get. The largest associations were for liver and endometrial cancer, each roughly halved.

One result ran the other way. Pancreatic cancer was more common after surgery, most clearly in younger adults, where the rate was about double. The reason is not known and the absolute numbers are small, but it should not be ignored.

This is observational, and people selected for surgery differ from those who are not. Still, it adds to the case that cancer risk is a reasonable part of the conversation about bariatric surgery, at any adult age, and that younger patients should not be told to wait on oncological grounds.

• Include long-term cancer risk in counselling for bariatric surgery, at any adult age.
• Expect the largest associated benefit for liver and endometrial cancer.
• Keep pancreatic symptoms in mind in follow-up after bariatric surgery, especially in younger patients.
• Do not delay referral of younger adults on the assumption that cancer benefit is age-limited.

Why it matters

It extends the cancer argument for bariatric surgery to younger adults and raises a pancreatic question nobody has answered.

Don't overread it

This was observational; it shows association, not that surgery prevents cancer, and the pancreatic signal is unexplained.

The statistics, in plain English

An incidence rate ratio of 0.81 means about 19 fewer cancers for every 100 expected without surgery. The confidence interval (0.77 to 0.85) is narrow because the cohort is huge, but a narrow interval does not remove confounding: healthier people may have been more likely to have surgery. The pancreatic result (2.21 in younger adults) is a single outcome among many tested, which makes chance more likely.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.