Genetic Testing in Cancer: What You Need to Know

• Dr. Aswin
• July 25, 2024

Decoding Your DNA: Are You at Risk?

One of the most powerful tools in modern oncology is Genetic Testing. While most cancers (90-95%) are "sporadic" (caused by aging, lifestyle, or environment), about 5-10% are "hereditary." This means a specific gene mutation—a glitch in the DNA code—is passed down from parent to child, significantly maximizing the risk of developing certain cancers.

Genetic testing allows us to see these potential threats years before cancer develops, offering the ultimate form of prevention.

"Your genes are not your destiny. Knowing your genetic risk is empowering—it shifts the power from the disease to the patient."

Somatic vs. Germline Testing: What's the Difference?

Patients are often confused between two types of DNA tests:

Major Hereditary Cancer Syndromes

There are many hereditary syndromes, but the most common ones include:

1. Hereditary Breast and Ovarian Cancer (HBOC)

Caused by mutations in BRCA1 and BRCA2 genes.
Risks: High risk of breast and ovarian cancer in women; prostate and breast cancer in men; pancreatic cancer in both.

2. Lynch Syndrome

Caused by mutations in genes like MLH1, MSH2, MSH6, PMS2.
Risks: Colorectal, Endometrial (Uterine), Stomach, and Ovarian cancers.

3. Others

Li-Fraumeni Syndrome (TP53): High risk of soft tissue sarcomas and brain tumors.
Cowden Syndrome (PTEN): Thyroid, breast, and uterine risks.

The Testing Process in India

Testing is simple but psycho-socially complex. It involves:

1. Pre-Test Counseling: A detailed review of your family tree (pedigree charting) to decide IF you need testing and WHICH genes to test.
2. Sample Collection: Usually a blood draw (3-5ml).
3. Next Generation Sequencing (NGS): Sophisticated labs analyze the DNA.
4. Post-Test Counseling: Explaining the results.

Understanding Your Results

Results are not just "Yes" or "No." They can be:

• Positive (Pathogenic): A cancer-causing mutation was found.
  Action: Increased surveillance (e.g., MRI breast), chemoprevention, or risk-reducing surgery.
• Negative (Benign): No known mutation found. Your risk is likely average or based on family history alone.
science doesn't know yet if it causes cancer.
Action: Do not act on this. We treat it as negative but monitor for future re-classification.

What If My Test is Negative?

A negative result is good news, but it doesn't always mean "zero risk."

• True Negative: If a known mutation exists in your family and you didn't inherit it, your risk is the same as the general population.
• Uninformative Negative: If no mutation is found in you, but you have a strong family history, there might be a gene we haven't discovered yet. In this case, we still recommend increased screening based on your family history.

The Future: Liquid Biopsies

Science is advancing rapidly. Soon, we may not need tissue biopsies. Liquid Biopsies allow us to detect cancer DNA circulating in the blood. This non-invasive method is already being used to monitor treatment response and is being researched for early detection.

Family Matters: Cascade Testing

If you test positive, your first-degree relatives (siblings, children, parents) have a 50% chance of having the same mutation. Testing them is called "Cascade Testing." It saves lives by catching high-risk individuals before they ever get cancer.

What Happens in a Genetic Counseling Session?

It is not just a blood test; it is a process. Here is what to expect with Dr. Aswin's team:

1. Family Tree Mapping: We draw a 3-generation pedigree. We look for "red flags": cancers at young ages (<50), rare cancers (male breast cancer), or multiple cancers in one person.
2. Risk Assessment: We use statistical models to calculate your specific probability of carrying a mutation.
3. Test Selection: Single gene (BRCA only) vs. Multi-gene Panel (30+ genes). Panels are now the standard because they catch more.
4. Insurance Approval: We help document the medical necessity for insurance coverage.

Financial Considerations

Genetic testing sounds expensive, but costs have dropped significantly (from lakhs to thousands). Many insurance plans now cover testing if there is a strong family history. We can help you navigate the paperwork.

The Emotional Impact

Waiting for genetic results is stressful. Remember:

• Knowledge is Power: Knowing gives you options (surveillance, medication).
• It's Not a Death Sentence: A positive result means higher risk, not that you have cancer right now. You can take action to prevent it.

Genes Beyond BRCA: A Quick Guide

FAQs: Privacy & Fear