Gastroenterology

Gastroenterology

Volume 138, Issue 5, May 2010, Pages 1697-1703.e2
Gastroenterology

Clinical—Alimentary Tract
Inflammatory Bowel Disease Confers a Lower Risk of Colorectal Cancer to Females Than to Males

https://doi.org/10.1053/j.gastro.2010.02.007Get rights and content

Background & Aims

Reported differences in cancer risk between male and female animals after chronic inflammation suggest that estrogen has inflammation-modifying properties. Little is known about these effects in human beings. Inflammatory bowel disease (IBD) is associated with an increased risk of colorectal cancer (CRC); we studied differences in inflammation-associated CRC between men and women patients with IBD.

Methods

By using a large population-based cohort (n = 7607) of individuals diagnosed with IBD from 1954 to 1989, we assessed the sex-specific incidence of CRC from 1960 to 2004. Incidence was determined within the cohort (modeled using Poisson regression) and compared with the general population (assessed as standardized incidence ratios) using data from national Swedish health and census registers.

Results

During 171,000 person-years of follow-up evaluation, 196 new cases of CRC were observed (123 in males, 73 in females). Males with IBD had a 60% higher risk of CRC (relative risk [RR], 1.6; 95% confidence interval [CI], 1.2–2.2) than females (cumulative incidence 40 years after IBD diagnosis, 8.3% vs 3.5%). Compared with the rate of CRC among the general population, in males with IBD the RR was 2.6 and the 95% CI was 2.2–3.1, whereas in females the RR was 1.9 and the 95% CI was 1.5–2.4. The effect of sex was limited to the period after 10 years of follow-up evaluation (RR, 0.8 before vs 2.2 after), and to patients diagnosed before age 45 (RR, 2.1 before vs 1.0 after).

Conclusions

IBD confers a lower risk of CRC to females than to males.

Section snippets

Setting

We performed a population-based cohort study including 3 large Swedish cohorts of patients with ulcerative colitis (UC) or Crohn's disease, with follow-up evaluation for vital status and cancer occurrence through national registers in which data have been recorded prospectively, as previously reported.8 The Swedish personal identification number system allowed for register linkages. The diagnosis of CRC was obtained through the Swedish National Cancer Register, which was started in 1958 and has

Overall Occurrence of CRC

In total, 7607 patients with IBD were followed up for a total of 171,000 person-years. During this time, 196 cases of CRC in 188 patients were registered, corresponding to an unadjusted overall incidence of 110 (95% confidence interval [CI], 99–131) cases per 100,000 person-years.

Among the 3936 men followed up for 87,424 person-years there were 118 cases of CRC (overall unadjusted incidence, 135/100,000 person-years). Among the 3671 women followed up for 84,390 person-years there were 70 cases

Discussion

The results of our study suggest that both in terms of relative and absolute risks, IBD entails a higher risk of CRC in males than in females, even when taking the underlying sex difference in the general population occurrence of CRC into account. Moreover, our results suggest that, at least in absolute terms, the sex difference is most pronounced in the IBD subset (UC pan-colitis) in which the risk of inflammation-related CRC is the highest. Our results thus are in keeping with recent results

References (40)

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Conflicts of interest The authors disclose no conflicts.

Funding Supported by the Swedish Medical Association, the Swedish Cancer Society.

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