How Does Family History of CRC Impact Risk for Patients With IBD?

Patients with IBD have an increased risk of CRC, and guidelines recommend annual colonoscopies for those with a first-degree relative with early-onset CRC, defined as CRC incidence before age 50. Since the last study that looked at the impact of family history of CRC, taking age of diagnosis into account, on CRC risk among patients with IBD in 1999, incidence of IBD and CRC have both increased, but the risk of CRC among patients with IBD has decreased. Asa H. Everhov, MD, of the Karolinska Institute, in Stockholm, Sweden, and colleagues said, “There is therefore a need to revisit the question of how family history of CRC in general affects the absolute and relative risks of CRC in more contemporary populations with IBD.” To determine this, Dr Everhov and colleagues conducted a nationwide, registry-based cohort study.

The study included 124,387 patients with IBD and 1,213,641 comparators, matched by age, sex, parish, and year, with data from the Swedish National Patient Register, the ESPRESSO cohort, the Swedish Cancer Register, the Cause of Death Register, and the Total Population Register. All comparators had no CRC, IBD, or colectomy at the start of follow-up. The primary outcome was incident CRC, defined as either a diagnosis of CRC in the National Cancer Register or CRC listed as the main/contributory cause of death in the National Cause of Death Register.

Total follow-up was 1,605,336 person-years for those with IBD and 16,189,588 person-years for the comparators. There was a total of 6% of participants overall who had at least one first-degree relative with CRC, with 5.9% having at least two first-degree relatives with CRC and having at least one first-degree relative with early-onset CRC. The CRC incident rate for patients with IBD was 1.17, compared to 0.88 for the comparators. For those patients with IBD who did not have family history of CRC, the CRC incident rate was 1.15, compared to 1.67 for those with any family history (0.82 and 1.87, respectively, for the comparators). For those patients with at least one first-degree relative with early-onset CRC, the CRC incident rate was 1.57 among patients with IBD and 1.50 among the comparators. For those patients with at least two first-degree relatives with CRC, the CRC incidence rate was 3.84 for patients with IBD and 3.70 for the comparators. This represents an increase of 2.69 cases per 1000 person-years for patients with IBD and at least two first-degree relatives with CRC compared with those with IBD and no family history, and an increase of 0.42 cases/1000 person-years for patients with IBD and a family history of early-onset CRC.

According to Dr Everhov and colleagues, these results show “the risk of CRC was increased in individuals with a family history of CRC, both in IBD and in the matched comparators,” and that the “largest absolute and relative risk increase in our main analysis was observed in patients with IBD and two or more first-degree relatives.” They added that these findings “raise the question if surveillance strategies should instead prioritize patients with multiple affected relatives,” compared to the current guidelines, which specify increased surveillance strategies for those patients with a family history of early-onset CRC.