One in two Australians will be diagnosed with cancer by the age of 85, so it is not uncommon for members of the same family to develop the disease.
Cancer can occur in families:
- in an unrelated way, which is most often the case
- because they have been exposed to the same environmental and lifestyle risk factors, such as too much sun, drinking alcohol or smoking,
- because there is an inherited faulty gene which increases the risk of cancer, but this is not common, or
- a combination of these different factors.
Only a small percentage of certain cancers (up to 5%) are due to an inherited faulty gene. A faulty gene increases the risk of cancer, but it does not mean every family member will develop the disease.
Cancer caused by an inherited faulty gene may be referred to as familial or family cancer, hereditary cancer or an inherited predisposition to cancer .
If you're concerned about your family's cancer history, call 13 11 20 or talk to your doctor who can refer you to a familial cancer centre.
Signs of familial cancer
Looking at the history of cancer on both sides of your family can help you understand the risk of the cancer developing due to an inherited faulty gene. It is good to know:
- The number of blood relatives who have had cancer – the higher the number, the greater the risk. Blood relatives do not include family members that are related by marriage.
- The ages of family members when they developed cancer – the younger they are, the more likely it is to be a result of inherited factors.
- The pattern of cancer in your family – the type of cancer and who it affects in your family are important. Some faulty genes can cause more than one type of cancer.
- If your family has a particular geographical/ethnic background – some inherited cancer genes are more common in Jewish or Eastern European ethnic groups.
Knowing this information can help your doctors estimate your risk of developing cancer. If you find out about any new diagnoses of cancer in your family, tell your doctor as it may impact their advice.
It is important to understand that some people who inherit a faulty gene which causes an increased risk of cancer never go on to develop cancer. If you are concerned, speak to your doctor.
Looking after yourself
Hearing that you have a higher risk of cancer compared to the general population can be a shock. You may find it difficult to cope with the increased possibility of developing the disease, or you may feel reassured and begin to make changes to your lifestyle and habits.
It is natural to want to know what is likely to happen, so you can plan for your future. But it is important to remember that family history and genetic testing only estimate the level of risk. It does not tell us who will get cancer or when they will develop it.
Talking about how you are feeling with your loved ones and trained health professionals, such as a counsellor or psychologist, can be helpful. It may make you feel more in control of your life.
Speak to a trusted cancer nurse
Genetic conditions and inherited cancers
Inherited faulty genes can increase the risk of developing certain types of cancer. This includes breast, ovarian and bowel cancer, and melanoma, among others.
To find out if you have inherited a faulty gene, you should speak to your doctor, who will determine whether you need a referral to a familial cancer centre . Call 13 11 20 for more information and support.
Most people diagnosed with breast cancer don’t have a family history of the disease. However, a small number of people may have inherited a gene fault that increases their breast cancer risk. Everyone inherits a set of genes from each parent, so they have two copies of each gene. Sometimes there is a fault in one copy of a gene. This fault is called a mutation or pathogenic variant.
The two most common gene mutations linked to breast cancer are the BRCA1 and BRCA2 genes. Other types include CDH1, PTEN, STK11, TP53, PALB2, ATM and CHEK2. People with an inherited BRCA1 or BRCA2 change are at increased risk of breast cancer. An inherited BRAC2 change may also increase the risk of prostate cancer.
Most people diagnosed with ovarian cancer do not have a family history of the disease, but some have inherited a faulty gene that increases the risk of developing ovarian cancer. Having an inherited faulty gene does not mean you will definitely develop ovarian cancer, and you can inherit a faulty gene without having a history of cancer in your family.
About 15–20% of people with ovarian cancer have an inherited fault in the BRCA1 or BRCA2 genes or other similar genes. The BRCA gene faults can also increase the risk of breast cancer.
Less commonly, a group of gene faults known as Lynch syndrome is associated with ovarian cancer and can also increase the risk of cancer of the uterus or bowel. BRCA faults can also increase the risk of prostate cancer.
Sometimes bowel cancer runs in families. If one or more of your close family members have had bowel cancer, it may increase your risk. This is especially the case if they were diagnosed before the age of 55, or if there are two or more close relatives on the same side of your family with bowel cancer. A family history of other cancers, such as endometrial (uterine) cancer, may also increase your risk of developing bowel cancer.
Some people have an inherited faulty gene that increases their risk of developing bowel cancer. These faulty genes cause a small number (about 5–6%) of bowel cancers. There are two main genetic conditions that occur in some families:
- Familial adenomatous polyposis (FAP) – this condition causes hundreds of polyps to form in the bowel. If these polyps are not removed, they may become cancerous.
- Lynch syndrome – this syndrome is characterised by a fault in the gene that helps the cell's DNA repair itself. It is also called Hereditary Non-Polyposis Colorectal Cancer (HNPCC).
Sometimes melanoma runs in families. Often, this is because family members have a similar skin type or a similar pattern of sun exposure in childhood. Only 1–2% of melanomas in Australia involve an inherited faulty gene. Some of these genes have been identified.
When two or more close relatives have been diagnosed with melanoma, especially if the person has been diagnosed with more than one melanoma on different areas of the skin and/or diagnosed with melanoma before the age of 40, then they may have an inherited faulty gene.
People with a strong family history of melanoma should protect and monitor their skin themselves, and have a professional skin check by a doctor every year from their early 20s. New moles after this age should be investigated.
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The information on this webpage was produced by Cancer Council Victoria (2022). This webpage was last updated in February 2022.