IBD patients with family cancer history more likely to develop colorectal cancer

People with inflammatory bowel disease (IBD) who have several close relatives with colorectal cancer are significantly more likely to develop the disease themselves. This is demonstrated by a new Swedish registry study from Karolinska Institutet, published in the journal Gastroenterology. The findings raise the question of whether future cancer screening guidelines should place greater emphasis on the number of cancer cases in a patient's family.

Current international guidelines for IBD patients emphasize whether a first-degree relative has developed colorectal cancer before the age of 50. However, our study shows that the number of cancer cases in the family may be a more important risk marker."

Åsa Everhov, senior consultant in surgery at Södersjukhuset and associate professor, Department of Medicine, Solna, Karolinska Institutet

Individuals with inflammatory bowel diseases such as Crohn's disease or ulcerative colitis are at an increased risk of developing cancer of the large intestine or rectum, known as colorectal cancer. Heredity is also a well-known risk factor. However, relatively few studies have examined how having first-degree relatives (parents, siblings or children) with colorectal cancer affects the cancer risk in people with IBD.

The new study included 124,387 people with IBD in Sweden between 1996 and 2023. They were compared with just over 1.2 million people from the general population and were followed for a median of eleven years. During this period, 1,882 people with IBD developed colorectal cancer.

2.6 times higher risk

The highest risk was observed in people with IBD who had two or more first-degree relatives with colorectal cancer. These individuals were approximately 2.6 times more likely to develop the disease than those with IBD who had no family history of cancer.

"By comparison, the risk was only just under 50 per cent higher among IBD patients with a first-degree relative who had developed colorectal cancer before the age of 50. This raises the question of whether the number of affected relatives should carry greater weight when assessing cancer risk," says Ola Olén, senior consultant in paediatric gastroenterology at Sachs' Children and Youth Hospital and adjunct professor at the Department of Medicine, Solna, Karolinska Institutet.

The researchers also found that people who had first-degree relatives with colorectal cancer had roughly the same absolute risk of developing the disease, regardless of whether they had IBD or not.

The study is based on register data from the Patient Register, the Cancer Register, the Cause of Death Register, the Multigenerational Register and the national ESPRESSO cohort, among others.

Funding for the research came from the Swedish Research Council, the Swedish Cancer Society, Vinnova, ALF funding from Region Stockholm, Karolinska Institutet and ERA PerMed, among others.