For women….Bowel cancer is twelve times more likely to cause death in a 60 year old woman as a car accident and it has a slightly lower chance of causing death than a heart attack over the next 10 years. Breast cancer is more common and is around twice as likely to cause death in women aged 60 than bowel cancer over the next 10 years.
For men… Bowel cancer is eight times as likely to cause death in a 60 year old man as a car accident but one-third as likely to cause death as a heart attack over the next 10 years. Prostate cancer is about half as likely to cause death in men aged 60 as bowel cancer over the next 10 years.
How does my family history affect my bowel cancer risk?
If you have a relative who got bowel cancer quite young (less than 55 years of age), or if you have more than one relative with bowel cancer on the same side of your family (eg your mother and your sister), it could be that you have a strong tendency for bowel cancer to run in your family. Sometimes this is due to genetic types that we know of called Familial Adenomatous Polyposis (FAP) or Hereditary Non-polyposis Colorectal Cancer (NPCC). These higher risk types occur in around 1% of the population and because of the higher risk of bowel cancer, FOB testing is not usually recommended.
Does FOB testing lower my chance of getting bowel cancer as well as my chance of dying from it?
One of the randomised trials of FOB testing showed that the risk of getting bowel cancer can be reduced after 18 years of regular testing (the Minnesota study). However, another study in Denmark (the Funen study) showed no difference in the rate of developing bowel cancer over the same period of time despite regular screening. The third study (Nottingham) did not continue testing for long enough to show this. Some people argue that the removal of polyps which could later become cancerous will lower the chance of cancer ever developing.
Why are there two different numbers quoted for lowering risk of dying from bowel cancer?
When the FOB trials were done, people were randomly assigned to receive the test or not. For ethical reasons, the completion of the tests was optional and the proportion of people who actually did the test varied in each of the studies. When the study results are combined statistically we can estimate how much FOB testing will reduce bowel cancer death rates (16%). This figure includes the cancer deaths in people who were offered testing and didn’t complete it, or perhaps only completed it some of the time (not every 2 years). However, the researchers noticed that in those people who did actually complete the tests the reduction in bowel cancer deaths was greater. The higher figure (25%) adjusts for participation in the screening and estimates the reduction in bowel cancer deaths if people did actually complete the FOB test every two years.
