The cause of cancer in the intestine is unknown despite extensive and continuing research. Patients with Crohn’s disease (CD) of the small and/or large intestine have an increased risk of developing cancer at these sites.
Most patients never develop cancer, but its early detection in patients at increased risk can lead to prompt and curative treatment. The risk should therefore not cause you great concern because if you have had extensive disease for 10 years or more, you will be offered regular screening and monitored very closely.
The risk is related to 2 main factors:
There appears to be some evidence that it occurs more frequently in chronically active disease than it does in previously active or intermittent disease.
Studies have shown that the chance of developing cancer of the colon rises steadily in all patients with the length of time the disease has been present. Several studies have been carried out to estimate the risk by following patients over a period of 10-40 years. Some failed to show an associated risk, but others predicted an increase which was twice that of the general population for developing colorectal cancer. If the disease is confined to the colon (large intestine), this risk is estimated at around 5 times greater.
The risk of small intestinal cancer has been estimated at around 6 times that of the general population, but as this is an extremely rare cancer in the general population, the risk in CD is still small.
(Please note, the above figures are only estimates and may vary among different studies according to referral centres and selection biases).
Cancers of the small intestine in CD tend to occur in areas affected by underlying inflammation. Most small intestinal tumours occur in the terminal ileum when severe inflammation, with consequent narrowing and stricture formation, has persisted. Cancer of the large intestine tends to occur when the right side of the colon is affected with associated strictures and/or fistulous disease.
Cancer may also be associated with long-standing perianal disease (ano-rectal fistulae, fissures, abscesses) which has not responded to conventional treatment.
These may be variable according to the site and extent of the cancer, but mostly show a general worsening of the symptoms associated with the disease:
Late symptoms may include:
After 10 years of disease, particularly in the colon, such symptoms should be taken seriously and discussed with your doctor.
As you approach the risk period (i.e. 10 years of extensive disease) your doctor will monitor you very closely for any changes. The type of monitoring will vary according to disease site:
If there are no strictures present a colonoscopy and multiple biopsies will be offered on a two-yearly basis.
If cancer is detected or a stricture appears highly suspicious, an operation will be necessary to remove it. This would usually involve cutting out (resecting) the affected area and rejoining the healthy bowel (anastomosis). Although the cancer, or the risk of it developing in that area, is removed, it does not provide a cure for the CD. However, with careful post-operative management, relapses can be prevented.
For severe, refractory (not responsive to treatment) perianal disease, removal of the colon (colectomy) and formation of an ileostomy may be indicated. A well-functioning ileostomy with appropriate support from stoma care nurses may be liberating from the misery of persistent fistulae, abscesses or pain and, thus, improve general quality of life. The fear of colorectal cancer is also removed.
If you experience any of the following please consult your doctor: