In recent years there has been increasing awareness that a tendency to develop cancer can sometimes be inherited. There have been numerous items on television or in newspapers. Naturally this has led many people who have affected relatives to wonder whether they have an increased risk themselves. This page has been written to help you if you do have these concerns. There is advice about what you should do if you are concerned.
There are several reasons why your doctor may feel that a referral to the Cancer Genetics Service is appropriate, for example:
- You may have a strong family history of cancer
- You may have been treated for cancer yourself
There are two important things to remember:
- Most cancer is not inherited.
Cancer usually occurs as a result of a combination of adverse factors. Some of these factors are understood - such as smoking and poor diet, whilst others are unknown. Cancer usually occurs in older people - after there has been time for the effects of these harmful factors to build up.
Cancer is very common. Cancer affects approximately 1 in 3 people during their lifetime. Therefore, in the average sized family it is not unusual to see 2 or 3 people with some form of cancer, purely by chance. In most cases the cancer risk to other family members is not significantly increased.
A small proportion of cancer is inherited or “familial”. It is believed that about 5 – 10% of many common cancers (such as breast, ovary and colon) are inherited. There is not usually any simple test to tell us whether a particular cancer is inherited, so we need to look at the family tree. When we assess a family history we look for certain “clues”.
- Several relatives with the same type of cancer
- Cancer occurring at an unusually young age
- More than one new cancer in the same person
- A recognised pattern of cancers, for example breast and ovary.
If you think that you may be at risk of inherited cancer you should discuss this with your GP.
What happens if my GP thinks I may have an increased risk of cancer?
Your GP may decide to refer you to the Peninsula Clinical Genetics Service. Sometimes it is possible to provide an answer in writing to your GP, but in many cases we will arrange an appointment to meet you. Usually we need to investigate the family history a little further. We draw your family tree and gather information about the cancers that have occurred in your family.
What is the purpose of a cancer genetics assessment?
- To assess whether there is an inherited tendency to cancer in the family
- To estimate your own level of risk compared with the general population
- To advise on whether any special screening is available or appropriate.
- To consider whether genetic testing is possible in your family.
Once you have been referred by your GP you will receive a letter from us and a request to complete the family history questionnaire enclosed with the letter. It is usually necessary to confirm details about a person’s cancer by checking their medical records. We will send you forms to pass onto to your affected relatives to seek their written permission to do this. We understand that this can sometimes be difficult but the more information we have the more accurate our assessment will be.
Please note that we do not contact any of your relatives directly or access medical details of surviving relatives without their permission.
People sometimes find it difficult to find out all the information to complete the family history sheet - they may have lost touch with their relatives for example. However, it is still important to return the family history sheet and a partially completed sheet is more useful than no sheet at all! If we do not hear from you, we will assume that you do not wish to be seen.
Once all this information is available we will assess whether there is evidence of a genetic predisposition to cancer in your family. This will help us decide whether you are at increased risk yourself and whether genetic testing is possible. You will then be offered an appointment either with one of our specialist genetic nurse counsellors or a consultant. Sometimes further appointments may be needed.
Can I have a Genetic Test?
If you have not had cancer yourself, but have a significant family history then genetic testing can usually only be offered if a misprint has already been identified in the family or if we first identify a genetic misprint in one of your affected relatives. In exceptional circumstances it may be possible to offer testing to someone who has not had cancer, but has a very close relative (parent, brother or sister or child) who has had cancer but there is no one affected by cancer in the family alive to test. More often genetic testing may not be possible if there are no surviving affected relatives in your family and there is no genetic sample stored.
Macmillan Cancer Support