The risk for certain types of malignancy in celiac disease (CD) patients has long been a cause for concern. Other types of cancers, such as breast cancer and lung cancer, may be less common in subjects with CD. Studies in the US and UK have pegged the overall increase in risk for malignancy at about 1.5 times higher in CD patients. A recent investigation of cancer risk associated with CD from Finland used the social institutions in place there to conduct a very large, population-based study.

The article, titled “Incidences of Malignancy in Diagnosed Celiac Patients: A Population-based Estimate” was published in the September, 2014 issue of The American Journal of Gastroenterology.  Using the nationwide registry of the Social Insurance Institution, which offers money to Finnish CD patients to help cover the additional costs of living gluten-free, and cross-referencing it with the Finnish Cancer Registry, which “covers 98% of diagnosed malignancies in Finland,” the authors, led by first-author Dr. Tuire Ilus, identified over 30 thousand CD patients, and 1,626 cases of malignancy in those patients. Using controls, the authors calculated the expected number of cancer cases and compared that to how many were observed in the database to determine the standardized incidence ratio (SIR). An SIR less than 1 means that the risk of cancer was lower in CD patients compared to controls, and an SIR greater than 1 would mean the risk was higher.

Overall, the authors found that CD patients actually had a somewhat smaller risk of malignancy than compared to controls (SIR of 0.94). When analyzed by gender, men had a statistically insignificant difference in risk compared to controls (SIR of 1.00) where women had an SIR of 0.89. When looking at cases 5 years or more after diagnosis however, CD patients’ risk of cancer was increased with an SIR of 1.31.

The authors also looked at specific kinds of cancer to see what the cohort of CD patients were more at risk for. The difference between men and women was explained by the significantly decreased risk of breast cancer. The risk of lung, pancreatic, renal, and bladder cancers were all reduced as well. However, the CD cohort’s SIR for small-intestinal cancers was more than 4 times greater than the control group’s. Risk of colon cancer was also increased (SIR of 1.35), especially after 5 years or more (SIR of 3.12).

The strength of this study comes from its very large size, thanks to Finland’s Social Insurance Institution and Cancer Registry, as well as their extremely high diagnosis rate; however, the authors do admit to some limitations. The data from the Social Insurance Institution was not sufficient to distinguish between cases of celiac disease and dermatitis herpetiformis. Also, other confounding factors were not investigated, such as smoking habits and weight. The decreased risk of lung cancer, for instance, may have been caused by patients with CD not smoking as much compared to controls, instead of being caused by any biological effect due to CD itself. Previous studies have indicated that CD patients smoke less than the general population, and this would also explain the decreased risk of renal and bladder cancers as well.

The authors conclude that overall, the risk for cancer was not increased in CD patients; however, after 5 years there was an increased risk. More specifically, the risk for non-Hodgkin lymphoma and small-intestinal cancers were increased significantly, though not as much as previous research indicated.

 The paper “Incidence of Malignancies in Diagnosed Celiac Patients: A Population-based Estimate” was published by the American Journal of Gastroenterology and can be found here.