Chapter 4: Understanding Targeted Therapy and Immunotherapy

Chapter 4: Understanding Targeted Therapy and Immunotherapy

How modern cancer treatments work — and why genomic profiling helps identify the right option for you.

Cancer treatment has evolved. While chemotherapy remains an important and effective tool, today’s oncologists also use targeted therapies and immunotherapies — treatments that are more precise and often more personalized.

Understanding how these treatments work can help you appreciate why your doctor recommends genomic testing as part of your care.

How Chemotherapy Works — and Why Newer Options Are Sometimes Considered

Chemotherapy attacks fast-growing cells, including cancer cells. It is powerful and often essential.

A simple analogy:

Chemotherapy is like turning off electricity for the entire house to stop a fire.

It affects the cancer, but it can also affect normal cells — which leads to side effects. This doesn’t make chemotherapy “bad.” It simply means that, when possible, doctors also look for more precise ways to treat the cancer. This is where targeted therapy and immunotherapy come in.

What Is Targeted Therapy?

Targeted therapies are medicines designed to act on specific genetic changes (biomarkers) in your cancer. These mutations are identified through genomic testing.

The "Faulty Wire" Analogy:

Imagine your tumor is a house with one faulty wire causing all the problems. Targeted therapy doesn’t shut down electricity to the entire house; it finds the exact wire causing the fault and fixes only that.

These treatments are powerful because they attack the root cause of the cancer’s growth. Some common mutations with matching targeted therapies include:

• EGFR
• ALK
• ROS1
• BRAF
• HER2
• KRAS (and many others)

Why should patients consider targeted therapy?

When the right mutation is present, targeted therapy may:

• Work more effectively than standard chemotherapy
• Cause fewer side effects
• Offer longer-lasting control of the disease
• Improve comfort and quality of life
• Provide options even when other treatments fail

Note: Targeted therapy only works if the matching mutation is found — which is why genomic testing is so important.

What Is Immunotherapy?

Immunotherapy works differently. Instead of targeting the cancer directly, it helps your immune system recognize and fight the cancer.

Cancer cells often hide from the immune system, almost like wearing a disguise. Immunotherapy helps remove that disguise so your immune cells can see and attack the cancer.

Comparing the two:

• Targeted therapy fixes the faulty wire inside the cancer cell.
• Immunotherapy trains the immune system to see the threat clearly and respond.

When Does Immunotherapy Work Best?

Immunotherapy is more likely to work when certain biomarkers are present. These help doctors understand how “visible” the cancer is:

BiomarkerWhat it Means MSI-HTumors struggle to repair DNA, making them easier for the immune system to detect.TMB-HighTumors with many mutations appear more “foreign” to the immune system.PD-L1 ExpressionA protein that helps cancer hide. High levels make certain drugs work particularly well.

Why should patients evaluate immunotherapy options?

When the right biomarkers are present, immunotherapy may:

• Offer long-lasting responses
• Work even after chemotherapy stops being effective
• Help the immune system keep the cancer under control
• Provide a treatment option with different side-effect profiles

How Genomic Profiling Helps Choose Between These Treatments

A genomic test acts like a “map” of your cancer’s biology. It helps your oncologist understand:

• ✔ Which mutations are present
• ✔ Whether targeted therapy is a good option
• ✔ Whether immunotherapy biomarkers (PD-L1, MSI, TMB) are present
• ✔ Whether certain treatments may not work
• ✔ Whether a combination of treatments is better
• ✔ Whether you qualify for clinical trials

The goal is simple: Choose the treatment that is most likely to work for your cancer, with the least unnecessary toxicity.

Why This Matters to You as a Patient

Chemotherapy, targeted therapy, and immunotherapy are all important. But when a mutation or immune signal can be targeted, it may offer:

• Greater precision
• Better results for the right patients
• A more personalized and less disruptive treatment experience

A Final Thought

Cancer treatment is no longer just about where the tumor started — it’s about what is happening inside it. Genomic profiling helps identify those internal signals so your doctor can choose the treatment that matches your cancer’s unique fingerprint.

Your oncologist will recommend the treatment that is safest and most effective for your individual condition. Trust their guidance — they are on your side.