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Comment on:Author response to: Effect of bariatric surgery on cancer risk: results from an emulated target trial using population-based data

Authors: K Sjöholm1, M Peltonen2,3, LMS Carlsson1, M Taube1

1Department of Molecular and Clinical Medicine; Institute of Medicine, Sahlgrenska Academy at University of Gothenburg, Sweden

2Department of Public Health and Welfare, Finnish Institute for Health and Welfare, Helsinki, Finland

3Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Sweden

Dear Editor,

We would like to thank Dr. Lazzati for the clarification regarding association between bariatric surgery and cancer events in the Swedish Obese Subjects (SOS) study.1

We agree that there are controversial results on the association between bariatric surgery and the risk of colorectal cancer (CRC). However, as pointed out in the response by Dr, Lazzati,1 it seems that reports indicating an increased incidence of CRC are authored by the same researchers and all based on estimated risk differences using non-standardized comparative groups derived from retrospective data.2-4

It is true that all the studies from Sweden, including the SOS study that we represent, capture cancer events from the Swedish National Cancer Register, so this is not the reason for the controversy. Instead the controversy most likely arises from important differences with respect to study design and statistical analysesreviewed in 5. The SOS study is a prospective, long-term study with a carefully matched obese control group, and our result that the risk of CRC is not increased after bariatric surgery is in agreement with other international publications on the topic.6, 7


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