Is Cancer Hereditary?

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Cancer is caused by different factors working together in intricate ways. One of these factors is genetic change. When cells experience faults in their DNA, it can cause them to grow and spread uncontrollably, which is a hallmark of cancer. 

Experts believe that multiple gene changes need to occur for a healthy cell to turn into a cancerous one. However, those who have inherited certain genetic mutations related to cancer might need fewer changes, placing them at a higher risk of developing the disease.

What Are Genetic Mutations?

Before we delve into whether cancer is hereditary, it is essential to understand some basics of genetics. Genes are sections or pieces of DNA that exist in our cells and contain sequences that act as instructions, telling cells what to do and thereby controlling how the body develops through our lifetime.

The body is constantly making new cells. This is achieved by cells copying and dividing themselves, but the process is complicated and mistakes happen. These mistakes in the copying process result in changes in the cell’s DNA sequence. 

Because DNA is like an instruction manual, with genes containing specific ‘pages’ of instructions, gene changes result in incorrect instructions. These changes or faults are called mutations. Changes in DNA can affect the proteins that control cell growth or that prevent cell self-destruction when damaged.  

Mutations can either be harmful, beneficial or have no effect. Our bodies have mechanisms to quickly repair or destroy DNA that has been changed or damaged, which is why many mutations do not end up affecting us. However, if something goes wrong in this process, and the mutations occur in important genes, mistakes can build up and cause disease. 

How Do Mutations Lead To Cancer? 

Genes play an essential role in controlling cell growth and reproduction, so mutations that influence this process can cause cells to grow uncontrollably, which is the key characteristic of cancer. There are two types of genes that can be mutated to develop cancer: oncogenes and tumour suppressor genes. 

Oncogenes promote the growth of cancer cells, while tumour suppressor genes block the growth of cancer cells. Mutations can cause oncogenes to become overactive or tumour suppressor genes to become inactive. 

Not all mutations will result in cancer. Cancer is generally the result of multiple genetic changes happening in a certain group of cells, causing them to become cancerous over time. This means that just having a mutation is not enough to cause cancer; other factors need to facilitate growth and development of mutated cells.

As a tumour grows, its cells continue to accumulate more mutations, with each person having a unique combination of DNA changes in their cancer. It can sometimes take years for these damaged cells to grow into a cancerous tumour that is large enough to cause symptoms or be detectable on medical scans. 

There are three causes of mutations, and by extension, of cancer:

  1. The most common is random or spontaneous copying errors that occur as part of your normal cell division process. 
  2. Environmental factors, which can either damage the genetic material or interfere with the repair process. 
  3. Inheriting a mutation from your parents.

Is Cancer Genetic Or Environmental?

The term "genetic" can be confusing as it is used to refer to both inherited genetic mutations and genetic mutations that occur during a person's lifetime. Either way, all cancers involve changes in genes which cause the disease to develop and progress. 

Mutations acquired during a person's lifetime usually occur spontaneously due to random cell replication errors. The longer you are alive, the more chances these errors have of occurring and building up, which is why most people get cancer at an older age. 

Genetic changes during your lifetime can also be influenced by exposure to environmental factors. Some environmental factors that can impact your chance of developing cancer include: 

  • Tobacco
  • Radiation
  • Viruses
  • Exposure to certain chemicals
  • A poor diet
  • Lack of physical activity
  • Chronic stress
  • Heavy alcohol consumption

How Inherited Genetic Mutations Work

Every person has two copies of each gene in their body: one inherited from our mother and one inherited from our father. Inherited genetic mutations can pass to you from either parent. Hereditary mutations can increase the risk of developing certain types of cancer, but are only responsible for a small percentage (around 5-10%) of all cancers. These germline mutations occur in reproductive cells (eggs and sperm), and can be passed onto children, unlike acquired mutations. 

Even though inherited mutations are a less common cause of cancer, they can have larger effects because the mutation is present in every cell of an individual rather than only in one area of the body. This can result in an increased likelihood of cancer at a younger age, cancer in multiple family members, rare cancers, and different but related cancers occurring in one person (e.g. breast and ovarian cancers). 

Which Cancers Are Hereditary?

There are several inherited genetic mutations that are associated with an increased risk of developing cancer. Breast cancer, stomach cancer, bowel cancer, and prostate cancer are examples of cancers with high genetic contributions. Some hereditary cancer syndromes are associated with an increased risk of developing multiple types of cancer. 

These hereditary gene changes should not be thought of as hereditary cancer, but rather as a hereditary predisposition which simply puts you at a higher risk. Even if your parents have a mutation, there is a chance you may not receive it. And even if it is passed on to you, it does not mean you will get cancer. 

BRCA1 And BRCA2 Genes

The most well-known inherited genetic mutations are those in the BRCA1 and BRCA2 genes, which are tumour suppressor genes. These genes occur in men and women, and mutations in these genes increase the risk of developing breast, ovarian, pancreatic and prostate cancers. 

Li-Fraumeni Syndrome

Another example of a hereditary predisposition is Li-Fraumeni syndrome, also caused by a mutation in a tumour suppressor gene (TP53). People with this gene fault are at a higher risk of developing several cancers, including breast, bone, acute myeloid leukaemia, soft tissue sarcoma, brain, and adrenal gland cancers.


How Can I Find Out My Risk Of Cancer? 

As cancer can affect healthy and unhealthy people, there is no way that we know of to ensure that you will never get cancer. However, there are things you can do to decrease your risk of developing cancer. This includes limiting exposure to environmental factors that cause mutations, as well as regular cancer screening. 

The earlier cancer is found, the earlier treatment can begin, which generally leads to a better prognosis. 

Individuals who are concerned about their risk of developing cancer due to family history can also undergo genetic testing and counselling. This process can identify whether you have inherited genetic mutations that increase the risk of developing certain types of cancer. 

The aim of genetic testing is to find people with inherited mutations so that they can receive the best cancer monitoring and prevention options for their situation. For example, more frequent colonoscopies, breast MRIs in addition to mammograms, or even risk-reducing surgery, depending on the cancer and individual factors. 

Does Cancer Run In Families?

Cancer is developed in a complex interplay of environmental, lifestyle, and genetic factors, including chance errors in our natural biology. While the majority of cancers are caused by environmental and lifestyle factors, a smaller percentage can be caused by inherited genetic mutations. However, having mutations that run in your family is not enough to cause cancer by itself. 

Regular screenings and a healthy lifestyle are the best ways to reduce the risk of developing cancer. If you are concerned about your chances of developing hereditary cancer, speak to your healthcare provider about genetic testing and cancer risk assessments.


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