Genes and cancer

If several members of your family have had cancer, you may be worried about your own risk and whether you have inherited a cancer gene. In this blog, our editor Elissia explains more about genes and cancer.

What are genes?

We inherit genes from our parents. Everyone has two copies of each gene – one from their mum and one from their dad.

There are genes in every cell in our body. They contain the information a cell needs to work properly. Our genes:

• control the process of making new cells
• tell cells how to repair damage
• tell a cell to die if it can’t be repaired or isn’t needed.

Genes and cancer

All cancers are caused by changes (mutations) in genes. There are two types of mutation:

• Acquired mutations – most cancers develop because of gene mutations that happen during a person’s lifetime (for example, mutations linked to getting older, tobacco, sunlight, hormones and diet).
• Inherited mutations – some people are born with a gene mutation that puts them at higher risk of getting certain types of cancer. These are called inherited cancer genes. 

Five facts about inherited cancer genes:

1. They are also called cancer predisposition genes or cancer susceptibility genes.
2. Inheriting a cancer gene doesn’t mean you have cancer.
3. Only a small number of cancers (up to 5 out of 100 cases, or 5%) are clearly linked to an inherited cancer gene.
4. Cancer genes can’t skip a generation. If you don’t inherit a gene, you can’t pass it on to your children.
5. Scientists have found inherited cancer genes for some common cancers. These include breast, bowel, ovary and womb cancers.

We have leaflets that you may find helpful if you are worried about your risk of developing bowel, breast, ovarian or prostate cancer.

If you are worried about cancer in your family

Remember most cancers aren’t caused by inherited cancer genes. 
Talk to your GP if you think cancer might run in your family. They may ask questions to assess your risk of cancer. 
Think about any close blood relatives who have had cancer. This means your parents, brothers, sisters, sons, daughters, aunts, uncles and grandparents.

Your family may have an inherited cancer gene if:

• two or more close blood relatives on the same side of the family had the same type of cancer
• members of your family under the age of 50 have had cancer
• certain cancers have occurred on the same side of the family
• a close relative has had more than one primary cancer (this means that they have had cancer twice, but the second cancer was a new cancer and not the first cancer spreading)
• you have a family history of cancer and have Polish, or Ashkenazi Jewish (Eastern European Jewish) ancestry.

It can be very difficult if you are worried about cancer in your family. If you think cancer might run in your family, speak to your GP. They can assess your risk, and arrange for you to see a genetics specialist if you need to. Talking to friends and family about your worries may also help. You can also talk to a genetic counsellor, or to our cancer support specialists by calling 0808 808 00 00.

Where can I find more information?

We have more information about cancer genetics in our booklet Cancer genetics, How cancer can sometimes run in families. It includes detailed information about genes and inherited cancers. We explain how genetic testing is done and some of the issues around having it. We also talk about risk-reducing treatments and screening, and offer support for coping with your cancer risk.

If you’re worried about a particular type of cancer in your family, we have a series of leaflets that you may find helpful:

• Are you worried about cancer?
• Are you worried about bowel cancer?
• Are you worried about breast cancer?
• Are you worried about ovarian cancer?
• Are you worried about prostate cancer?

Each leaflet gives information about cancer risk, what we know about the causes of that cancer type and support on how you may be able to reduce your risk.

We also have an online information tool you can use if you’re worried about your risk of breast or ovarian cancer. You can use the tool to help check your risk.

To see what else Macmillan's cancer information team has been blogging about, please visit our blog home page! You can subscribe to receive our blogs by email or RSS too.

We're with you every step of the way

The Macmillan team is here to help. Our cancer support specialists can answer your questions, offer support, or simply listen if you need a chat. Call us free on 0808 808 00 00.

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