In a population-based cohort study from Sweden and Denmark of patients with inflammatory bowel disease (IBD) during 1969-2017 and matched reference individuals from the general population, Ola Olén, Jonas F Ludvigsson and colleagues found that IBD patients had an increased risk of small bowel cancer.
The excess risks were especially high in Crohn's disease (a subtype of IBD) and for adenocarcinomas (a type of small bowel cancer), but the absolute risk increases were low, corresponding to one extra case of small bowel cancer in 385 Crohn's disease patients or in 500 ulcerative colitis patients followed for 10 years. The study was recently published in Gut.
Earlier studies of inflammatory bowel disease (IBD) and small bowel cancer have shown highly varying risk estimates. Some studies have reported 30-70 times higher risks for small bowel cancer, but these studies may have suffered from bias.
“Our results confirm that earlier studies have overestimated the risk of small bowel cancer in IBD,” says lead author, Dr. Ola Olén, Department of Medicine, Solna, Karolinska Institutet.
Since earlier studies often showed increased risks of small bowel cancer just around the date of IBD diagnosis, the dating of the IBD onset was important. Through linkage between the Swedish Patient register and the ESPRESSO study (“Through the Epidemiology Strengthened by histoPathology Reports in Sweden) study , the researchers were able to better define the date of IBD diagnosis. The fact that the Swedish and Danish researchers were able to better define the onset of IBD has likely influenced the results. The collaboration with Danish researchers increased the number of patients with IBD and the statistical power, allowing researchers to calculate precise risk estimates and to study subgroups of small bowel cancer.
“This study yields new knowledge. For instance we were able to demonstrate that risk factors, previously linked to colorectal cancer in IBD, are also associated with small bowel cancer”, says senior author, Professor Jonas F Ludvigsson, pediatrician at Örebro University Hospital, and professor at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.
“In all, we found a 9-fold increased risk of small bowel cancer in IBD, and a 7-fold increased risk of dying from small bowel cancer, but high excess risks were primarily seen during the first year after IBD diagnosis”, adds Ludvigsson. “To the individual patients with IBD, the risk of small bowel cancer is low.”
Source: Karolinska Institutet