Is Cancer Genetic?

What causes cancer?

Cancer is a complex group of diseases that have a variety of causes, and it affects 1 in 3 people in the United States. While cancer is a genetic disease, it does not have a single cause because the interaction of many different factors like genes, the environment, and individual risk factors contributes to a cancer diagnosis.

Your body is made up of trillions of cells that continue to regenerate over the course of your life. Normally, the body makes new cells to replace the old ones, but genetic changes inside the cells may disrupt this process. This abnormal change in the gene is called a mutation. Cancer develops from these genetic mutations that cause the cells in your body to grow uncontrollably.

Most genetic mutations aren’t harmful on their own. However, the accumulation of genetic mutations over many years can turn healthy cells into cancerous cells. Most cancers happen as a result of this process.

What is the difference between hereditary versus genetic?

The main difference between the two is that hereditary diseases can be carried from one family generation to another. However, genetic disease means there is always a genetic mutation that can either be hereditary or not.

Over 90% of cancers are caused by a genetic mutation

What causes genetic mutations?

Genetic mutations can occur in two ways:

An inherited gene mutation

• An abnormal gene was passed on to you from your parents, which can turn into more mutations, leading to cancer. Very few cancers are the result of a hereditary mutation. 

An acquired gene mutation

• Gene mutations that develop after birth are acquired and can be a result of lifestyle choices and risk factors. Most cancers are caused by this type of mutation.

Is cancer hereditary?

All cancers originate from a genetic mutation within the cells. While gene mutations can be passed down from parents to children, cancer itself cannot be passed down.

In the small percentage of cases where cancer is caused by an inherited gene mutation, it is known as “inherited cancer,” “hereditary cancer syndrome,” or “family cancer syndrome.”

Only 5% to 10% of all cancers are from inherited gene mutations

Most cancers are not caused by an inherited mutation, rather they are caused by mutations that occur over time as a result of aging, environmental exposures, viruses, or lifestyle habits. If your family has a history of cancer or has a gene mutation linked to cancer, it does not mean you will develop cancer, but you may be at greater risk of developing cancer.

What are the risk factors for cancer?

A risk factor is anything that may increase your chance of developing cancer, but it doesn’t cause the disease. The risk factors for cancer include lifestyle, environmental, and genetic factors, such as:

• Age (older people are at higher risk)
• Radiation exposure (X-rays, radon, ultraviolet radiation from sunlight)
• Exposure to cancer-causing substances (asbestos, diesel exhaust, and second-hand smoking)
• Family history of cancer
• Certain infections (human papillomavirus [HPV] and Epstein-Barr virus [EBV] among others)

Healthy lifestyle choices can possibly reduce your chances of getting cancer. Some lifestyle choices that are associated with increased risk for cancer include:

• Smoking
• Alcohol consumption
• Obesity
• Lack of exercise 
• Eating an unhealthy diet (red and processed meat, high-sugar drinks and snacks, and highly processed foods)

If there are many cases of cancer occurring in one family, it is most often due to chance or a common risk factor like smoking. Less often, there is an inherited gene mutation that runs in the family that can be linked to cancer and that is known as “inherited cancer.”

There are specific factors that make inherited cancer more likely:

• Cancer in a parent or sibling or 2 relatives with cancer on the same side of the family 
• Many cases of the same type of cancer (especially if it is an uncommon or rare type of cancer)
• Cancers occurring at a younger age 
• More than one type of cancer in a person (a person having both breast and ovarian cancer)
• Cancers occurring in a pair of organs (both eyes, both kidneys, or both breasts)
• More than one childhood cancer in siblings 
• Cancer occurring in a sex that is not usually affected (breast cancer in a man)
• Cancer occurring across many generations

Your healthcare provider can help you assess the risk of inherited cancer in your family.

What are some examples of inherited cancer?

Here are just a few examples of the most well-known genetic mutations that can be passed on to children: 

• BRCA1 or BRCA2
  • Women and men with BRCA1 or BRCA2 genetic mutations have a significantly higher risk of developing breast and other cancers than those without the mutations. Other cancers associated with the BRCA1 and BRCA2 genes include ovarian, pancreatic, prostate, and melanoma.
• Mutations in specific mismatch repair genes that cause Lynch syndrome
  • This is a hereditary disorder that can put someone at a higher risk of developing colon, endometrial, and other cancers such as stomach, pancreas, urinary tract, or brain. 
• Li-Fraumeni syndrome
  • This is a rare inherited syndrome that often develops at a young age, and can lead to the development of a number of cancers, including sarcoma (such as osteosarcoma and soft-tissue sarcomas), leukemia, brain (central nervous system) cancers, cancer of the adrenal cortex, and breast cancer.