Coeliac disease causes the lining of the small bowel to wither away. This is due to an autoimmune disorder due to an allergy to gluten. Only people who are genetically predisposed will develop the disorder.
It has been well known for many years that small bowel lymphoma (a highly specific type of cancer) occurs in patients with coeliac disease. Other cancers have been described as well but no-one really knows the actual risks of any of these cancers. It is thought that the overall risk of cancer is increased by about 50% in patients with coeliac disease.
Coeliac disease occurs in anything around 1-2% of the population although many people may have abnormal blood tests but no actual overt disease.
What the Study Showed
In the American Journal of Gastroenterology a large study of over 32,000 patients with coeliac disease in Finland was carried out. These patients were followed up for many years to see what the risk of developing cancer was.
In the first five years after the diagnosis of coeliac disease was made there was no increased risk of cancer. Beyond this time, the risk increased very slightly. For non-Hodgkin’s lymphoma the risk was twice as high as in the general population. For small intestinal cancer, which is in any case very rare, the risk was four times higher than the general population.
Various other cancers were more common also. Colon cancer was 35% more common and basal cell carcinoma of the skin was about 10% more common.
Curiously, there was a decrease in the likelihood of lung cancer by 40%, breast cancer by 30% and pancreatic cancer by 30%.
The decreased risk of these cancers is interesting, but perhaps most important, the increased risk of non-Hodgkin’s lymphoma is rather lower than had previously been thought.
In this study all people with a suspected diagnosis of coeliac disease had undergone duodenal biopsy showing the typical subtotal villous atrophy with crypt hyperplasia, which is a hallmark of the condition. In the small number of people who presented with skin manifestations of coeliac disease (dermatitis herpetiformis), a biopsy sample of skin was taken to confirm the typical granular IgA deposits. This means that the accuracy of the study is very high.
I find these results very reassuring. They confirm what we already know, but tell us that cancer risks are lower than previously thought. Nonetheless, what we do not know is how important it is to be very strict with dietary control. We believe this is important and we still strongly recommend to our patients to manage their coeliac disease properly. Cancer is not the only complication that can occur. People with uncontrolled coeliac have problems with absorption of calcium and therefore they develop thinning of the bones and osteoporosis. For this reason alone it is very important to maintain a strict gluten-free diet once coeliac disease is diagnosed.