You might have heard that if anyone in your family has cancer, then the chances of you getting a cancer is high.
Is this really true? Can one really inherit cancer?
The short answer is: yes. A genetic cancer test can help find out whether one has the cancer-causing gene. But, there are many factors that determine whether you are at risk for cancer. So, before you consider genetic testing for cancer, there are few things you need to know about cancer and how gene testing for cancer helps.
What are inherited cancers?
A very simple way to look at cancer is that it is a disease in which the cells grow abnormally and destroy the body. Most of us know that we may be at risk of cancer due to smoking and alcohol and poor lifestyle choices. There are also many environmental factors such as sunlight exposure, radiation exposure and chemicals that put us at risk of developing cancer.
When cancer is caused by such factors and only affects specific cells in the body, then these cancer cells are the ones that mutate and not the normal cells. So in such types of cancers, the mutation is not passed on.
However, there are about 5% of cancers that are passed on through the genes, which means that every cell in the body carries the gene mutation at birth.
What happens if you are born with a gene mutation?
Let us explain taking the example of BRCA1 and BRCA2 genes. Genetic testing for these genes was made famous by the American actor Angelina Jolie who decided to go for an elective mastectomy (breast removal) after she tested positive for mutations in these genes.
A harmful mutation in BRCA1 and BRCA2 genes in women can not only increase the risk of breast cancer and/or ovarian cancer but also fallopian tube cancer and peritoneal cancer. Men with mutations in these genes are also at risk of breast cancer.
Some studies also suggest that BRCA1 and BRCA2 mutations may be associated with prostate, pancreatic and stomach cancers.
Everyone has these two genes and if there is a mutation in these genes, these mutations are passed down through generations in a dominant pattern.
So mutations in BRCA1 and BRCA2 genes will cause breast cancer?
The presence of a mutation alone does not mean that the person will get cancer. It means that regardless of whether the person develops cancer or not, both men and women who inherit the mutation can pass it on to their sons and daughters.
So if a person has this gene mutation, then there is a 50% chance that the gene can be passed on to their kids regardless of the gender of the child. A certain family history may also indicate whether the cancer is hereditary. Some of the things to watch out for are:
- Breast cancer under 50 years
- Cancer in both breasts
- Breast and ovarian cancer detected within the same family
- Multiple breast cancers in the family
- Breast cancer in a male family member
In such cases, or in cases where a sibling or family member has been found with a BRCA1 or BRCA2 mutation, then genetic testing may be recommended.
How to find out whether cancer runs in the family?
Here are some of the factors that indicate there might be a high risk of inheriting a cancerous gene mutation in certain families:
- First-degree relatives, which means the parents, siblings or children, have cancer
- Many relatives on one side of the family have or had the same type of cancer
- Many of the cancers in the family are linked to single gene mutation (like we saw in the case of the BRCA1 and BRCA2 genes)
- A family member has or had more than one type of cancer
- Cancer occurred at a younger age than what is typical for a specific type of cancer
- A family member with a rare cancer
- Certain ethnic groups
- Conditions that are linked to an inherited cancer (such as polyps in the colon)
Obviously, you can also come to know about gene mutation if another member in the family has already done genetic testing and found out about it.
Genetic testing for cancer
Genetic testing for cancer looks for a specific inherited gene mutation that can cause cancer. This type of test involves an analysis of their DNA from a blood sample or a sample of a person’s tissue, such as saliva or cheek swab. It is a predictive test which is used to find out the risk of a person getting a certain type of cancer.
So if anyone in the family or close relative is diagnosed with hereditary cancers, then undergoing the test can help a person to identify their relative risk of cancer-based on their genes.
The idea is to be able to be emotionally, physically and financially prepared to deal with cancer in the future, if needed. The early warning can also help those who wish to make lifestyle changes to lower their risk of developing cancer or to take steps to reduce its impact on their lives. For example, a high risk of breast cancer may indicate a need to begin breast cancer screening at a younger age.
To avoid fear and uncertainty, it is important to go for genetic counseling prior to and after the test. This will not only help you understand the degree of risk and to know how to interpret the results. That is why if you are looking to book a genetic test for cancer, then chose one that offers such counseling and detailed guidance every step of the way.
Genetic Testing For Cancer: Genetic Counselor Answers FAQs
Hodgson S. Mechanisms of inherited cancer susceptibility. J Zhejiang Univ Sci B. 2008 Jan;9(1):1-4.
Rahner N, Steinke V. Hereditary cancer syndromes. Dtsch Arztebl Int. 2008 Oct;105(41):706-14.
Rahman N. Mainstreaming genetic testing of cancer predisposition genes. Clin Med (Lond). 2014 Aug;14(4):436-9.
Hamilton R. Genetics: breast cancer as an exemplar. Nurs Clin North Am. 2009 Sep;44(3):327-38.
Lynch JA, Venne V, Berse B. Genetic tests to identify risk for breast cancer. Semin Oncol Nurs. 2015 May;31(2):100-7.
Brose MS, Rebbeck TR, Calzone KA, et al.Cancer risk estimates for BRCA1 mutation carriers identified in a risk evaluation program. J Natl Cancer Inst. 2002;94(18):1365-72.
Cavanagh H, Rogers KM. The role of BRCA1 and BRCA2 mutations in prostate, pancreatic and stomach cancers.Hered Cancer Clin Pract. 2015 Aug 1;13(1):16