Is Cancer Genetic? Understanding Hereditary Cancer Risk

At a Glance! 

• All cancers involve DNA changes, but most are not inherited. Only about 5% to 10% of cancers are hereditary.
• Inherited predisposition can be suggested by family history, early onset of cancer, and multiple affected relatives.
• The common inherited cancer genes include BRCA1, BRCA2, MLH1, MSH2, MSH6, PMS2, TP53, PTEN, APC, PALB2 and ATM.
• Genetic testing can help assess inherited risk, but it cannot predict cancer with certainty.
• Genetic counseling helps interpret findings and guide screening decisions.
• A positive result means higher risk, not the actual diagnosis of cancer.
• A negative result does not eliminate all cancer risk.
• A VUS is inconclusive and should not guide medical decisions.

Is Cancer Genetic? Understanding Hereditary Cancer Risk

A woman waits in a hospital waiting room, thinking about her own cancer risk after learning that her mother has been diagnosed with cancer for the second time. A young man realizes that his father, uncle, and grandfather all had colon cancer at a relatively young age, below the age of fifty. These are common moments, and they usually lead to the same question: is cancer genetic? The truth of the matter is far more complicated and goes beyond just a yes or no answer. Most types of cancer occur due to aging, environmental exposures, lifestyle factors, and random DNA replication errors.

In contrast, a small percentage of cancers occur due to the presence of gene mutations passed on by family members. Knowing the difference is crucial, as it will determine the choice of genetic tests, screening guidelines, and whether emotional anxiety is warranted. This blog breaks down what "genetic cancer" really means, which genes are involved, how family history factors in, and what practical steps a person can take if hereditary cancer runs in their family. 

What Does "Genetic" Mean in Cancer?

To answer the core question: all cancer is genetic, but not all cancer is inherited. This distinction is key to understanding your personal risk, as genetic changes play a role in cancer development, but only some of these changes are passed from parents to children. 

Cancer begins when changes, called mutations, build up in a cell's DNA and cause it to grow uncontrollably. Nearly all cancers involve some form of genetic mutation at the cellular level, but that does not mean all cancer is inherited. There are two very different categories worth separating clearly.

1. Inherited (Germline) Mutations

Inherited mutations are genetic changes present from birth. They are passed from a parent to a child and exist in almost every cell of the body. These inherited changes can increase a person's risk of developing certain cancers.

Hereditary cancer develops when a person inherits a cancer-predisposing genetic mutation. People with inherited cancer-related gene changes may have a higher chance of developing specific cancers, sometimes at a younger age or with a stronger family history of cancer.

2. Acquired (Somatic) Mutations

Acquired mutations develop during a person's lifetime and are not passed from parents to children. They also cannot be passed on to future generations because they are not present in reproductive cells. The mutations result from various influences such as aging, smoking, UV light exposure, certain infections, environmental factors, or errors made during the cell division process.

According to cancer research data, only a small percentage of cancers are linked to inherited genetic changes. For instance, about 5-10% of breast cancers are considered hereditary. This is due to inherited genetic mutations, while the rest are due to other causes. Similarly, most other cancers are caused by factors other than inherited pathogenic variants. 

In simple terms, cancer is a genetic disorder since it involves changes in DNA, but most cancers are not inherited. Some people are genetically predisposed to certain cancers while others are not.

Also read: 

https://redcliffelabs.com/myhealth/cancer/understanding-cancer-with-faqs-answered-by-a-doctor-get-detailed-information-on-cancer-its-diagnosis-and-treatment/

How Much of Cancer Is Hereditary?

Only about 5% to 10% of all cancers are considered hereditary, meaning they occur because a person inherits a cancer-related gene mutation from a parent. The remaining cancers usually result from genetic changes acquired throughout life.

Understanding the 3 Types of Cancer Risk

Types of Cancer Risk	Meaning	Example
Hereditary Cancer (5-10%)	Caused directly by a single pathogenic gene variant passed from parent to child.	Specific gene variants like BRCA1 or BRCA2 are passed down in germline DNA.
Familial Cancer (15-20%)	Cancer occurs more frequently in a family than expected by chance, but no single inherited gene mutation is identified.	Shared environmental factors, lifestyle, or minor combination gene effects.
Sporadic Cancer (70-80%)	Caused by acquired DNA mutations over a lifetime (aging, environment, lifestyle).	The most common type; occurs randomly without a strong family pattern.

Having a family member with cancer does not always mean the cancer was inherited. The kind of cancer, age when diagnosed, and number of people who have the same kind of cancer within one's family can guide doctors on what could be responsible for that condition.

Causes: Why Do Some Families Carry Higher Cancer Risk?

Hereditary cancer risk usually results from inherited changes in specific genes, especially those involved in controlling cell growth and repairing damaged DNA.

Normally, tumor suppressor genes help prevent uncontrolled cell growth. When a person inherits a pathogenic variant in one of these genes, the body may have fewer protective mechanisms against cancer-causing changes.

The most widely studied examples are BRCA1 and BRCA2, which are associated with increased risks of breast, ovarian, prostate, and pancreatic cancers.

Other hereditary cancer-related genes include:

• PALB2: Partner and localizer of BRCA2, strongly linked to hereditary breast and pancreatic cancers. 
• TP53: Responsible for Li-Fraumeni syndrome; linked to early-onset breast cancer, sarcomas, brain tumors, and adrenocortical carcinoma. 
• PTEN: Causes Cowden syndrome; associated with breast, thyroid, and endometrial cancers. 
• ATM: Increases baseline susceptibility to breast and pancreatic cancers. 
• MLH1, MSH2, MSH6, PMS2 (Lynch syndrome): Mismatch repair genes responsible for Lynch syndrome (colorectal, endometrial, ovarian, and stomach cancers). 

Note: Although inheriting a cancer-predisposing mutation increases one's chances of developing the disease, it does not make the onset of cancer inevitable. This idea is called incomplete penetrance in genetics, which means the disease may or may not develop depending on environmental influences and other genetic factors. 

How Are Cancer Genes Passed Through Families?

Many hereditary cancer syndromes follow an autosomal dominant inheritance pattern. This means a person only needs to inherit one altered copy of a gene from either parent to have an increased risk.

If one parent has a harmful mutation, then each child may have a 50% chance of inheriting that mutation.

However, inheritance of a mutation does not mean that cancer will definitely occur: other contributing factors like age, environmental exposures, hormonal influences, and additional acquired genetic mutations play a major role in whether cancer actually develops.

What Family History Suggests a Higher Risk of Hereditary Cancer?

A family history may suggest an increased risk of hereditary cancer if:

• Cancer occurs at a younger age (often before age 50).
• Two or more close relatives have the same or related types of cancer.
• Cancer appears across multiple generations on the same side of the family.
• A person develops more than one primary cancer.
• Rare cancers occur in the family.
• Male breast cancer is present in the family.

A family history may be considered less suggestive of hereditary cancer when:

• Only one relative has cancer, especially if diagnosed at an older age.
• The cancer type is common, and there is no clear pattern within the family.
• There is no history of the same or related cancers across multiple generations.

Common Hereditary Cancer Syndromes At a Glance

Syndrome	Genes Involved	Associated Cancers
Hereditary Breast and Ovarian Cancer (HBOC)	BRCA1, BRCA2	Breast, ovarian, prostate, pancreatic, melanoma
Lynch Syndrome	MLH1, MSH2, MSH6, PMS2	Colorectal, endometrial (uterine), ovarian, stomach, biliary tract
Li-Fraumeni Syndrome	TP53	Soft tissue/bone sarcoma, breast, brain, adrenocortical carcinoma
Cowden Syndrome	PTEN	Breast, thyroid, endometrial, kidney
Familial Adenomatous Polyposis	APC	Colorectal (hundreds to thousands of polyps)

Can Genetic Testing Identify Cancer Risk?

Yes, genetic testing can be used to find out whether an individual has particular genetic mutations that may increase the risk of certain cancers. But it should be noted that genetic testing cannot predict with certainty whether someone will develop cancer. 

In genetic testing, a blood or saliva sample is analyzed for any genetic mutations linked to hereditary cancer syndromes. Genetic testing is recommended to people who have a strong family history of cancer, early-onset cancer, several affected members with cancer, or particular cancer syndromes known to be caused by hereditary mutations. 

The results of genetic testing are generally interpreted in three ways:

Test Result	Meaning
Positive result	A harmful gene mutation associated with increased cancer risk is identified. It does not mean the person has cancer, but their risk may be higher.
Negative result	No known harmful mutation is detected. A negative result is most informative if a specific mutation was already identified in an affected family member.
Variant of uncertain significance (VUS)	A change in a gene is found, but there is not enough evidence to determine whether it affects cancer risk.

If a hereditary cancer-related mutation is identified, healthcare professionals may recommend personalized screening plans, preventive measures, or testing for close family members who may also carry the same mutation. 

Common Myths vs. Facts

Myth 1: If there is cancer on the father's side, then I cannot get it.

Fact: Autosomal dominant cancer genes are equally transmitted from fathers or mothers to both sons and daughters. 

Myth 2: If the genetic test comes out negative, then I am 100% safe from cancer.

Fact: Genetic testing does not detect sporadic cancer. Over 70% of cancers are sporadic and are caused by aging and lifestyle.

Myth 3: If I test positive for a mutation, I will definitely get cancer.

Fact: Positive test results indicate increased risk, not a guaranteed diagnosis. Proactive surveillance and appropriate risk-reduction strategies can help detect cancers early and may improve outcomes. 

Also read: 

https://redcliffelabs.com/myhealth/blood-test/understanding-the-role-of-blood-tests-for-diagnosing-bone-cancer/

What Should You Do If Cancer Runs in Your Family?

Having several family members diagnosed with cancer can be concerning, but it does not mean cancer is inevitable.

If cancer appears to run in your family, consider the following steps:

• Know your family history: Note the type of cancer, age at diagnosis, and relationship of affected family members.
• Discuss your risk with your doctor: They can assess whether your family history suggests hereditary cancer syndrome.
• Consider genetic counseling: A genetic counselor can help determine whether genetic testing is appropriate and explain the possible benefits and limitations.
• Follow recommended screening: If your risk is higher, your doctor may advise starting screenings earlier or having them more frequently.
• Inform close family members: If an inherited mutation is identified, other relatives may also benefit from counselling or testing.

Remember: Having a family history of cancer increases risk for some people, but it does not mean cancer is inevitable. Early awareness allows for informed decisions and timely preventive care.

Prevention and Risk Reduction

Genetic testing is a tool to help you understand and manage your risk of cancer, but it is not a diagnosis or a prediction that you will get cancer. Being proactive can help support early detection and informed healthcare decisions, whatever your results are, positive, negative or inconclusive.

1. Get recommended cancer screenings. If you have an inherited pathogenic variant associated with cancer, or a strong family history of cancer, your doctor may advise earlier or more frequent screening than that recommended for the general population.
2. Get genetic counselling before and after the test. A genetic counsellor can help you understand whether testing is appropriate, explain your results and discuss the most appropriate screening or prevention strategies.
3. Inform biological relatives. Family members might also want to undergo genetic counselling or testing, as they might have inherited the same gene mutation.
4. Adopt healthy lifestyle habits: Avoid tobacco, limit or avoid alcohol, maintain a healthy body weight, eat a balanced diet, and stay physically active. While lifestyle changes cannot remove an inherited mutation, they can significantly reduce overall baseline cancer risk. 
5. Attend regular follow-ups. Guidelines for screening and risk reduction will vary according to your age, personal health status, and family history.
6. Choose clinically validated genetic testing. If genetic testing is recommended, it should be conducted by an accredited clinical lab and interpreted by healthcare professionals. Consumer genetic tests may not assess all cancer-related genes and should not be used alone to make medical decisions.

Conclusion

Is cancer genetic? Yes, but with important context. All cancers result from genetic alterations within cells, but only 5% to 10% are caused by inherited gene mutations passed down through families.

Having a family history of cancer or carrying an inherited gene mutation indicates an increased risk. It does not guarantee that you will develop cancer. Understanding your family medical history, seeking expert genetic counselling, following recommended screening programs, and maintaining a healthy lifestyle can help you make informed decisions and support your long-term health.

Stay Informed About Your Health with Preventive Cancer Screening

Knowing your family medical history and personal risk factors will help you make informed decisions about your health. 

At Redcliffe Labs, preventive health packages and cancer screening options help individuals monitor important health markers and stay proactive about their well-being.

You can explore options such as:

• Cancer Screening Packages: Designed to assess important cancer-related health markers based on individual risk factors. Examples include breast cancer screening, cervical cancer screening, prostate cancer screening, and genetic cancer risk assessment (when recommended).
• Comprehensive Health Checkups: Help evaluate overall health parameters that support preventive care. Examples include Full Body Checkups, Diabetes Screening, Heart Health Checkups, and Women’s or Men’s Wellness Packages.

With every test at Redcliffe Labs, you also avail of 4x Value Benefits, which include:

• Smart Reports: Easy-to-understand health insights and trends.
• Expert Report Guidance: Support to understand results and recommended next steps.
• AI Health Assistance: Quick support for health-related queries.
• Personalized Health Plans: Lifestyle recommendations based on your health goals.

Preventive screening can help you understand your health status and make informed decisions with your healthcare provider. 

FAQs

1. Is every cancer inherited from parents?

No, even though cancers are genetic disorders. About 5% to 10% of cancers are inherited conditions resulting from genetic mutations passed down from one's parents. The majority of cancers result from gene changes occurring during a person's lifetime because of aging, environmental exposures, lifestyle factors, or random DNA replication errors. 

2. Does having a family history of cancer mean I will develop cancer?

No, not necessarily. Having a family history of cancer raises your risk of developing cancer, but it does not guarantee that you are going to have cancer. Your risk of developing cancer depends on a number of factors like type of cancer, number of relatives who have cancer, inherited genetic mutations, age and environmental factors, among others.

3. Who should consider genetic testing for hereditary cancer?

You might need to undergo genetic testing if you have a strong family history of cancer or if cancers in your family were diagnosed at a young age. Testing may also be considered if a person has developed more than one primary cancer or if a relative has been confirmed to carry an inherited cancer-related gene mutation.

4. What cancers are commonly linked to inherited gene mutations?

Genetic mutations are common in breast, ovarian, colon, prostate, pancreatic, uterine, and certain rare cancers. Mutations in genes such as BRCA1, BRCA2, TP53, and mismatch repair genes associated with Lynch syndrome can increase the risk of certain cancers.

5. Can genetic testing tell if I will definitely get cancer?

No. Genetic tests reveal the mutations in inherited genes that raise the risks for developing cancer; however, the tests cannot predict the exact chances of developing cancer. There are cases when patients with inherited mutations do not develop any cancer, while those who lack these mutations have acquired genetic changes that lead to cancers.

6. What should I do if hereditary cancer runs in my family?

The first step is to collect information about your family members with cancer in terms of the type of the disease and the age of onset. Then consult your healthcare provider or genetic counsellor about the chances of cancer. If recommended, undergo genetic testing and follow personalized screening plans. Maintaining a healthy lifestyle can also help reduce your overall cancer risk. 

7. Can hereditary cancer be prevented?

While gene mutations are unpreventable due to genetics, early identification can help manage the risk. Regular screening, genetic counselling, preventive medical options when appropriate, and healthy lifestyle habits such as avoiding tobacco, limiting alcohol, maintaining a healthy weight, and staying physically active can support early detection and better health outcomes.