TOPLINE

Individuals with a family history of colorectal cancer (CRC) had an increased risk for CRC irrespective of whether they had inflammatory bowel disease (IBD) or not, and the greatest increase in the risk was observed among those with two or more first-degree relatives diagnosed with CRC.

METHODOLOGY

• Researchers conducted a register-based matched cohort study to assess whether a family history of CRC affects the risk for CRC in populations with IBD.
• They included 124,387 patients with IBD (median age, 41 years; 49% women) and 1,213,641 matched comparators from the general population (median age, 40 years; 49% women) between 1996 and 2023 in Sweden, of whom 74,122 were diagnosed with ulcerative colitis, 41,062 were diagnosed with Crohn's disease, and 9203 had IBD unclassified at diagnosis.
• Having a first-degree relative — defined as parents, children, or siblings — with exposure to CRC was noted. Patients were classified on the basis of the number of affected first-degree relatives (none, one, one or more, or two or more) and the age at diagnosis in any relative (< 50 vs ≥ 50 years).
• The primary outcome was incident CRC, defined as a diagnosis of CRC or CRC recorded as a cause of death in national registries. The median follow-up duration was 11 years.

TAKEAWAY

• Overall, 6% of participants in both the IBD and comparator groups had at least one first-degree relative with CRC. During follow-up, 1882 CRC events were reported in the IBD group (incidence rate, 1.17 per 1000 person-years) and 14,177 were reported in the comparator group (incidence rate, 0.88 per 1000 person-years).
• Among patients with IBD, the adjusted incidence rate ratio for CRC was 2.59 (95% CI, 1.42-4.27) in those with two or more affected first-degree relatives and 1.47 (95% CI, 0.79-2.47) in those with at least one first-degree relative diagnosed before the age of 50 years, compared with those without a family history. In the matched comparators, the corresponding incidence rate ratios were 2.89 (95% CI, 2.40-3.44) and 1.78 (95% CI, 1.45-2.16), respectively.
• The incidence of CRC was highest, with significant increases observed among patients with ulcerative colitis who had two or more affected first-degree relatives (incidence rate, 4.08 cases per 1000 person-years).
• Among individuals with any family history of CRC vs those without, the risk for CRC was higher in those with IBD (hazard ratio [HR], 1.31; 95% CI, 1.10-1.56) and the matched comparators (HR, 2.09; 95% CI, 1.97-2.21). Among individuals without a family history, the absolute risk for CRC after 10 years was higher in those with IBD than in the matched comparators (0.83% vs 0.63%; P < .001).

IN PRACTICE

"Current AGA [American Gastroenterological Association] and ECCO [European Crohn's and Colitis Organisation] guidelines advise special attention to patients with a family history of early-onset CRC. Our findings raise the question of whether such intensified surveillance should instead be prioritized for patients with ≥ 2 affected relatives," the authors wrote.

SOURCE

This study was led by Åsa H. Everhov, Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden. It was published online on September 03, 2026, in Gastroenterology.

LIMITATIONS

The misclassification of variables, particularly Montreal stage information obtained through diagnostic coding, may have affected accuracy. Disparities in the incidence of CRC based on a family history could have been affected by variations in colonoscopy frequency.

DISCLOSURES

This study was supported by grants from the Swedish Research Council, the Regional Agreement on Medical Training and Clinical Research between the Stockholm County Council and Karolinska Institutet, Karolinska Institutet Region Stockholm funds, the Swedish Cancer Society, Vinnova, and ERA PerMed ScandRA. Several authors reported receiving grants, fees for lectures, and speaker fees or serving on advisory boards of different companies and organisations.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.