# Effects of bariatric surgery on cancer incidence in obese patients in Sweden (Swedish Obese Subjects Study): a prospective, controlled intervention trial

Source: https://onco.cc/key-papers/paper-sjostrom-lancet-oncol/  
OnCo record `paper-sjostrom-lancet-oncol` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Paper cited by one technology page, indexed on Europe PMC as PubMed record 19556163 and published in The Lancet Oncology; the citing page links this DOI, which is how the record was matched.

## Summary

Background: Obesity is a risk factor for cancer. Intentional weight loss in the obese might protect against malignancy, but evidence is limited. To our knowledge, the Swedish Obese Subjects (SOS) study is the first intervention trial in the obese population to provide prospective, controlled cancer-incidence data.

Methods: The SOS study started in 1987 and involved 2010 obese patients (body-mass index [BMI] >or=34 kg/m(2) in men, and >or=38 kg/m(2) in women) who underwent bariatric surgery and 2037 contemporaneously matched obese controls, who received conventional treatment. While the main endpoint of SOS was overall mortality, the main outcome of this exploratory report was cancer incidence until Dec 31, 2005. Cancer follow-up rate was 99.9% and the median follow-up time was 10.9 years (range 0-18.1 years).

Findings: Bariatric surgery resulted in a sustained mean weight reduction of 19.9 kg (SD 15.6 kg) over 10 years, whereas the mean weight change in controls was a gain of 1.3 kg (SD 13.7 kg). The number of first-time cancers after inclusion was lower in the surgery group (n=117) than in the control group (n=169; HR 0.67, 95% CI 0.53-0.85, p=0.0009). The sex-treatment interaction p value was 0.054. In women, the number of first-time cancers after inclusion was lower in the surgery group (n=79) than in the control group (n=130; HR 0.58, 0.44-0.77; p=0.0001), whereas there was no effect of surgery in men (38 in the surgery group vs 39 in the control group; HR 0.97, 0.62-1.52; p=0.90). Similar results were obtained after exclusion of all cancer cases during the first 3 years of the intervention.

Interpretation: Bariatric surgery was associated with reduced cancer incidence in obese women but not in obese men.

Funding: Swedish Research Council, Swedish Foundation for Strategic Research, Swedish Federal Government under the LUA/ALF agreement, Hoffmann La Roche, Cederoths, AstraZeneca, Sanofi-Aventis, Ethicon Endosurgery.

Indexed on Europe PMC as PubMed record 19556163 (DOI 10.1016/s1470-2045(09)70159-7). Matched by DOI alone: one technology page cites this DOI among its external links (the pages are listed under Related), and this page was written so that the citation resolves inside OnCo. No figure has been checked by an editor.

## Fields

- Kind: Key paper
- Last checked: 2026-09-22
- Tags: europepmc-ingest
- Journal: The Lancet Oncology
- Year: 2009
- DOI: 10.1016/s1470-2045(09)70159-7
- Authors: Sjöström L, Gummesson A, Sjöström CD, et al.
- What it means: One technology page on OnCo cites this paper by its DOI; this record gives the citation a page of its own so a reader can follow it without leaving OnCo. Read the abstract above alongside the citing page listed under Related; the record was created automatically from the Europe PMC entry and its figures have not been checked by hand.
- Caveats: Matched to the citing OnCo records by DOI alone; the summary reproduces the Europe PMC abstract and no figure has been verified against the full paper.

## Sources

- Lancet Oncol 2009: https://doi.org/10.1016/s1470-2045(09)70159-7
- PubMed: https://pubmed.ncbi.nlm.nih.gov/19556163/
- Europe PMC: https://europepmc.org/article/MED/19556163

## Connected records

- technologies: [Bariatric surgery and cancer incidence](https://onco.cc/technologies/bariatric-surgery-cancer-incidence/)
- journals: [The Lancet Oncology](https://onco.cc/journals/lancet-oncology/)

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