What Is Genetic Testing for Cancer
Genetic testing for cancer looks for DNA changes that may increase cancer risk or guide treatment decisions.
There are two main types:
- Germline testing – looks for inherited mutations.
- Somatic (tumor) testing – looks for mutations inside cancer cells.
These tests help doctors personalize care.
Learn more:
Biomarkers in Cancer Explained
https://helping4cancer.com/biomarkers-in-cancer-explained/
Germline Genetic Testing (Inherited Risk)
Germline testing looks for inherited mutations passed down in families.
These mutations are present in every cell of the body.
Common Inherited Cancer Genes
- BRCA1 and BRCA2 – linked to breast, ovarian, prostate cancers
- Lynch syndrome genes (MLH1, MSH2, MSH6, PMS2) – linked to colon and endometrial cancer
- TP53 – linked to multiple cancer types
- APC – linked to familial adenomatous polyposis
People with inherited mutations may have:
- Higher lifetime cancer risk
- Earlier onset of cancer
- Increased risk of multiple cancers
Testing may guide:
- Preventive screening
- Risk-reducing surgery
- Family member testing
Somatic Genetic Testing (Tumor Testing)
Somatic testing examines DNA changes in cancer cells.
These mutations are not inherited.
They help guide treatment choices.
Examples include:
- EGFR mutations in lung cancer
- BRAF mutations in melanoma and colon cancer
- KRAS mutations in colorectal cancer
- HER2 amplification in breast cancer
This testing supports targeted therapy decisions.
Learn more:
Cancer Treatment Explained
https://helping4cancer.com/cancer-treatment-explained/
Why Genetic Testing Is Important
Genetic testing helps:
- Identify inherited cancer risk
- Select targeted therapy
- Determine eligibility for immunotherapy
- Avoid ineffective treatments
- Guide family risk assessment
It is a key part of precision oncology.
Who Should Consider Genetic Testing
Doctors may recommend testing if a person has:
- Cancer diagnosed at a young age
- Multiple cancers
- Strong family history of cancer
- Rare cancer types
- Known family mutation
A genetic counselor often helps interpret results.
What the Results Mean
Genetic test results may show:
- Positive result – a mutation was found
- Negative result – no known mutation found
- Variant of uncertain significance (VUS) – unclear meaning
Results do not always guarantee cancer will develop.
They indicate risk, not certainty.
Does Genetic Testing Mean You Have Cancer
No.
Inherited mutation does not mean cancer is present.
It means risk may be higher.
Regular screening and preventive strategies can reduce risk.
Learn more:
Cancer Prevention Explained
https://helping4cancer.com/cancer-prevention/
How Genetic Testing Is Done
Testing usually involves:
- Blood sample
- Saliva sample
- Tumor biopsy (for somatic testing)
Results may take several weeks.
Ethical and Emotional Considerations
Genetic testing may raise questions about:
- Insurance
- Family impact
- Emotional stress
In many countries, laws protect against genetic discrimination.
Genetic counseling helps navigate these concerns.
Key Takeaways
Genetic testing looks for DNA changes linked to cancer risk or treatment response.
There are two main types: inherited (germline) and tumor-based (somatic).
Testing helps personalize screening and therapy.
Results guide prevention, treatment, and family decisions.
It is central to modern precision medicine.
External References
National Cancer Institute – Genetic Testing for Cancer Risk
https://www.cancer.gov/about-cancer/causes-prevention/genetics/genetic-testing-fact-sheet
National Cancer Institute – Tumor DNA Sequencing
https://www.cancer.gov/about-cancer/treatment/types/precision-medicine
American Cancer Society
https://www.cancer.org/
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