People who are overweight or obese are more likely to develop colorectal (bowel) cancer. Because obesity (bariatric) surgery causes weight loss, it might also reduce the risk of developing colorectal cancer. However, a previous study from Scandinavia suggested that obesity surgery may have the opposite effect and increase the risk of colorectal cancer. A recent study of ours using English data did not confirm that colorectal cancer is linked to obesity surgery. However, in this study, patients who underwent bariatric surgery were only followed for around 3 years, which is not enough time for colorectal cancer to develop. Because non-cancerous tumours of the bowel, called colorectal polyps or adenomas develop first and then progress to colorectal cancer, we now propose to study risk of colorectal polyp development, instead of colorectal cancer. Polyps are detected and removed during bowel examinations such as colonoscopy. Clinical Practice Research Datalink data will be used to identify obese patients who have or have not undergone obesity surgery and compare the occurrence of polyps in both groups. Knowledge of whether obesity surgery is associated with increased polyp risk is important to understand future colorectal cancer risk and colonoscopy needs for patients who have undergone obesity surgery.
There is inconclusive evidence of an association between obesity surgery and long-term colorectal cancer (CRC) risk from separate studies in Scandinavia and England, which is partly related to the small number of CRC cases and short follow-up time after obesity surgery. The benign colorectal adenoma (natural history for development 1-3 years) is a recognised biomarker of CRC risk (Kinzler and Vogelstein, 1996, O'Brien et al., 1990) allowing a shorter follow-up period in a cohort study. We propose to use CPRD in order to explore colorectal adenoma risk after obesity surgery. This will be achieved through: 1) Initial non-parametric estimation of the probability of adenoma development in obese patients who had bariatric surgery and for obese patients who did not have bariatric surgery; 2) risk-adjusted survival analysis investigating the time from obesity surgery to adenoma; and 3) risk-adjusted binary analysis of adenoma development (yes/no) for obese patients with/without obesity surgery. If colorectal adenoma risk is elevated after obesity surgery, it will make the case for a study of the effectiveness of colonoscopic surveillance after obesity surgery for reduction in CRC risk. We will also examine the association between obesity surgery and obesity-related cancers (e.g. CRC, esophagus, endometrium or kidney).
Time to colorectal adenoma
- Colorectal adenoma
Secondary outcomes will be:
- Colorectal cancer
- Breast cancer
- Cancer of oesophagus
- Kidney cancer
- Endometrial cancer
- Ovarian cancer
- Cancer of the pancreas
- Upper stomach cancer
- Myeloma
Mark Hull - Chief Investigator - University of Leeds
Ariadni Aravani - Corresponding Applicant - University of Leeds
Amy Downing - Collaborator - University of Leeds
Eva Morris - Collaborator - University of Leeds
Mar Pujades Rodriguez - Collaborator - University of Leeds
HES Admitted Patient Care;ONS Death Registration Data;Patient Level Index of Multiple Deprivation