The old adage that you can choose your friends but not your family holds true when looking at your cancer risks.

Today people live for longer than at any other time in history. For instance in the 19th century, more babies died from disease, men and children died early working in the mines, plagues carried off the frail, women died in childbirth, and 40 was considered a ripe old age!

So cancer did still kill people back then but it killed less people because people died of other things long before they were ever at risk of a cancer. Today more people live until they are over 70, but 1 in 4 people over 70 will have a cancer.

1 in 4 people over 70 will have a cancer.

This is not due to an increase in cancer it is due to changes in cells and the inability of our bodies to kill or clean these abnormal cells.

It is not uncommon for more than one member of a family to have cancer. Cancer can occur in families:

  • By chance (most common)
  • Because family members have risk factors in common (such as environmental and lifestyle influences)
  • Because there is an inherited faulty gene causing an increased chance of cancer (uncommon)

How do I know if my family carries a faulty gene?

Trying to find information about cancers in your family and how to deal with them can be difficult. It is important to know your family history on both your mother’s and father’s side of the family. Even the faulty gene for ‘female’ cancers like breast and ovarian can be inherited from your father.

Only a small amount of some cancers (up to 5%) are due to a faulty gene which is inherited from either your father or mother. This is called a familial cancer. This can also be described as an inherited risk of cancer. The faulty gene increases the risk of cancer, but it certainly does not mean every family member must develop the cancer.

Clues that the cancer that runs in your family may be due to an inherited faulty gene include:

  • Number of relatives from your bloodline who have had cancer: The more blood relatives who have had cancer (particularly clusters of breast, ovarian and/or bowel cancer), the more likely the cancer is due to an inherited faulty gene.
  • A young age when the familial cancers occur: The younger a person is when they developed cancer (compared to what is expected in the general community) the more likely it is to be due to inherited factors.
  • Pattern of different cancers in the family: The type of cancer a person has and who it affects in the family are important. In some families, all patients may develop the same type of cancer, such as breast or bowel cancer. In other families, different sorts of cancer will cluster together (e.g. breast, ovarian or bowel cancer, and cancer of the uterus). This happens because some faulty genes can cause more than one type of cancer.

The more clues that are present, the more likely it is that there is an inherited faulty gene in the family causing the higher than usual chance of getting cancer. But this does not mean you will develop the cancer, just that you have an increased risk and need to be more vigilant with screening.

What should I do if I have a family history of cancer?

It is important to investigate your family history. You can find out what types of cancer your relatives have had and how old each person was when they developed cancer. It is also important to document a complete family history so you can see the family members not affected by cancer. Your family history of cancer can change over time as the members get older and more family members are born, so it is important to keep your doctor updated about any new cancer diagnosed in your family.

Family counselling and genetic counselling services

Genetic counselling services give people information about their chance of developing cancer based on their family history. These specialists can spend time discussing ways that may help reduce the chance of you developing cancer and how you can be vigilant. It may be that genetic testing is possible, particularly if a member of the family who has cancer can be tested.

This is only carried out after the advantages and disadvantages of testing for the patient and their family are discussed.

After female gender and advancing age, a positive family history of cancer is the strongest risk factor in developing Breast Cancer. In most cases there is not a long and extensive history of cancer present (more than four relatives in the same line). However in some families there is a strong hereditary line of cancer characterised by cancer in both breasts, young age at onset, and clustering of different cancers with breast (primarily ovarian and male Breast Cancer). Only less than 5% of all Breast Cancers will be due to these genes, which are known as BRCA1 and BRCA2. Others which are much less well known are TP53, PTEN/MMAC1, and STK11. There is testing available for the BRCA 1 and 2 genes for patients with a significant family history.

Managing these patients and families is highly specialised and requires communication between breast specialists and genetic specialists.

If you think you may be at risk of carrying one of these mutations you should discuss it with your doctor and be seen in a specialist breast unit.