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Cancer Genetics

Is cancer hereditary? Understand more about the genetics of cancer

Only a total of about 10% of all cancer cases are associated with mutations genetically passed on from one member of the family to another. It is important to understand that the mere presence of a gene that has the potential to cause cancer does not imply that the person will develop cancer in the future. People who carry the genes might be predisposed to a certain type of cancer, or they have a greater risk of developing cancer as compared to the rest of the population.

Picture of cancer cell which invades healthy tissues

Facts about genetic mutations:

There is a 50% likelihood for children who have inherited a genetic mutation to develop cancer at some point during their lives. There are a number of medical conditions and rare hereditary syndromes that are linked with a greater risk of the development of cancer in an individual. For instance, a genetic disorder known as neurofibromatosis increases the chance of the development of fibrosarcoma, rhabdomyosarcoma and various other forms of cancer. In case of a positive diagnosis of Down’s syndrome in children, there is a greater risk for the development of leukemia. Another rare genetic disorder known as Blood syndrome is linked with a greater risk of the development of some carcinomas, leukemia as well as lymphoma.

Genetic mutations:

Within the last few years, breakthrough discoveries have been made that help us understand genetic mutations more. We are closer to understanding how genetic mutations actually increase the chances of developing certain forms of cancer. Specific tests have been developed in order to discover the mutations which are typically associated with colon, breast and ovarian cancers. It has been discovered that the mutations occurring in the BRCA1 and BRCA2 genes frequently raise the risks of development of ovarian and breast cancers, especially in specific ethnic groups such as the Ashkenazi Jewish masses.

Specific mutations:

Mutations can cause an increase in the lifetime risk of the development of cancers such as ovarian cancer. According to statistics, the increase is from 1.7% in case of the general population, to a range of about 16 to 60% in case of women having mutations in the BRCA1 or BRCA2 genes. It must also be noted that men having mutations associated with the BRCA1 and BRCA2 genes can also have an increased risk of the development of breast cancer and prostate cancer. This is more frequently observed in case of BRCA2 mutations. Other forms of cancers that are linked with the alterations and mutations of the BRCA2 genes are pancreatic, gallbladder, stomach and bile duct cancers, as well as melanomas and lymphomas in both men and women. If the mutations of the BRCA genes are diagnosed and detected at an early stage, women can reduce the risk of cancer development with the help of immediate preventive surgical procedures for the removal of their ovaries and breasts.

Genetic testing: when should it be done?

Genetic testing[1] is an expensive and difficult procedure, and it is not a routine test at all. If you have a family history of cancer especially of multiple types, then this may be a good option for you. Just carrying a cancer gene does not mean that you may develop the condition, it makes a person more likely to develop a certain type of cancer. Cancer genes can remain dormant for a person’s whole life, or they may become activated and cause cancer growth.

Advantages of genetic tests:

Certain genetic testing can also help discover conditions passed from one generation to the next. For example, it can help explain the risk of the development of colon cancer in susceptible people. Individuals diagnosed with PAP, or Familial Adenomatous Polyposis can develop numerous polyps during the early stages of their lives and thus have almost a 100% risk of the development of colon cancer at some point during their lives. The second condition is known as the HNPCC, or the Hereditary Non-polyposis Colon Cancer, also called the Lynch syndrome. This syndrome increases the risk of developing colonic cancer up to 80%, as well as cancers associated with the stomach, endometrium, ovaries as well as several other organs. Patients with HNPCC also develop numerous polyps, but not to the same extent as the ones developed at an early stage in patients with PAP. Preventive surgeries can significantly reduce the risks of colon cancer development in patients of HNPCC and PAP if intervention is done at an early stage.

The decision to test an individual for  cancer having a genetic disposition is rather complicated. It is important to consult a genetic counselor because these professionals are trained to navigate and guide people through the procedure, at every single step. Genetic counselors provide adequate information and reassurance to people who are considering the test, in order to help them cope with possibilities of a positive diagnosis. These professionals, apart from providing psychological preparation, also provide patients with all the information related to the risks and benefits of taking the tests.

Genetic counselors are also responsible for helping patients and their family members adjust in case of a positive diagnosis, and in arranging measures necessary for screening and prevention. The test is just a blood test, but patients considering this test are overburdened with emotional trauma and require assistance and encouragement to proceed with it. Genetic counselors are extremely well versed in terms of information and reassurance, and are there to provide emotional support and confidence to patients in order to prepare them for the impending results.

Additional Resources:

National Cancer Institute. Cancer and the Environment: What You Need to Know, What You Can Do.   Access at: www.xmarks.com/site/cissecure.nci.nih.gov/ncipubs/

This booklet addresses concerns about the connection between cancer and exposure to toxic substances in the environment, including tobacco, alcohol, medical drugs, fibers, pesticides, and a variety of other chemicals. The reader will learn which types of substances are known carcinogens and what can be done to reduce exposure to them.

Daniel, Rosy, with Rachel Ellis. 2006. The Cancer Prevention Book: The Holistic Plan to Reduce Your Risk of Cancer  London: Simon & Schuster.

The author is a British physician specializing in holistic care for cancer patients. The book provides thorough explanations on cancer-causing lifestyle factors and covers self-examinations, screening tests, and early detection. It also includes a “self-help” chapter, which explains the mind/body/spirit connection and advises how to strengthen the mind and impprove emotional and physical health.

Runowicz, Carolyn D., Sheldon H. Cherry, and Dianne Lange. 2004. The Answer to Cancer. Emmaus, PA: Rodaie.

This book was written for people who want to avoid ever getting cancer, arrest precancerous changes, or prevent a recurrence. The authors are two physicians, one of them a cancer survivor herself.

This article was originally published on 7/12/2014 and last revision and update of it was 9/14/2015.