Gastrointestinal cancers are those that occur in the digestive system – that is the oesophagus, stomach, small bowel, pancreas and the large bowel – also called the colon and sometimes colorectum. The most common of these is bowel cancer.
Familial Gastrointestinal Cancer is the cancer that runs in families. Some types of Familial Gastrointestinal Cancer are inherited, this is where there is a known cancer syndrome.
Everyone has a risk of developing cancer but most cancer is not familial, ie it does not run in families. A small proportion of cancer (about 10-15 %) is thought to be due to inherited factors. In New Zealand the chance of developing bowel cancer by the time you are 75y of age is 6%. Sometimes there is a family history but the diagnosis occurred at an older age and there is no clear pattern from parent to child. Although the cancer may appear to be more common than you would expect to see in these families this may not be due to inherited factors. It can be due to chance and shared environmental factors – such as diet, smoking and exercise as families tend to have similar habits.
Sometimes there is a really clear family history with more than one generation affected and diagnoses occurring at a young age (in genetics under 50y is considered young). Having a parent, brother, sister or child with cancer may increase your chance of developing a cancer, particularly if they were young when first diagnosed. In a small number of families there is an inherited mutation (gene problem) that increases your chance of developing cancer.
Many people over estimate the chance of developing cancer and it is important that if you are concerned you seek expert advice as to the likelihood of developing cancer for you and other family members.