Genomic Testing and Biomarkers in Cancer Treatment: What Most People Miss

In modern oncology, genomic testing and biomarker testing are central to cancer treatment decisions across breast cancer, colorectal cancer, colon cancer, lung cancer, and more. But many cancer patients (and even oncologists) don’t realize how much critical information in these reports is often overlooked.

Most genomics and biomarker reports are generated by software, not interpreted by humans. They highlight the very well-known mutations tied to your specific cancer type—but that’s not always where the real value is. 

What Is Biomarker Testing and Why It Matters

Biomarker testing and genetic testing analyze tumor DNA to guide targeted therapy, chemotherapy, and immunotherapy for cancer. These tests identify mutations that can be matched with anticancer drugs or clinical trials.

This is a cornerstone of precision oncology. The goal is simple: match the right drug to the right tumor biology.

But this process depends entirely on how well the data is interpreted.

Why Genomics Reports Miss Critical Cancer Treatment Options

Most reports prioritize mutations that are:

• Common for that specific cancer type
• Well documented in existing research
• Directly linked to known drugs or clinical trials

This approach sounds logical—but it often ignores mutations that are highly actionable but less common.

For example, mutations typically associated with breast cancer or lung cancer may appear in melanoma, colorectal cancer, or other tumors. These can still respond to targeted therapy, even though they will not be flagged at the top of the report.

This is where valuable treatment opportunities are frequently missed.

The Problem with “Variants of Unknown Significance”

Another major issue in cancer genomics is the category called “variant of unknown significance” (VUS).

These are mutations that haven’t been extensively studied. As a result, they are usually ignored.

But many of these variants clearly disrupt protein function—especially when they truncate proteins (cause a premature stop or a "frameshift") or cause major structural changes. In cancer biology, that means the pathway is broken.

And broken pathways can often be targeted with existing cancer therapy, including drugs originally developed for other cancer types.

Why Variant Allele Fraction (VAF) Is Critical

One of the most overlooked numbers in any genomics report is the variant allele fraction (VAF).

VAF tells you how much of the tumor carries a specific mutation.

• A mutation with 0.2% VAF affects almost none of the tumor
• A mutation with 50–80% VAF affects most of the tumor

This matters because even the best targeted therapy won’t work if it only applies to a tiny fraction of cancer cells. It can be the best drug possible and have a 100% kill rate with virtually no side effects, but if it only works on 0.2% of your tumor it won't significantly benefit you.

Yet VAF is rarely emphasized in reports—and often overlooked in cancer care.

What This Means for Cancer Patients

Whether you are dealing with breast cancer, colon cancer, brain cancer, small cell lung cancer, or any other type, your genomics report likely contains far more actionable information than what’s highlighted.

To get the most out of genomic testing:

• Review the full report—not just the summary
• Look beyond labeled biomarkers
• Pay attention to VAF percentages
• Consider mutations outside your cancer type

Cancer treatment is no longer just about chemotherapy or surgery. It’s about understanding tumor biology in detail.

And in many cases, the difference between average and optimized care comes down to how well that data is interpreted.

Disclaimer:  This content is for educational purposes only and is not medical advice. It does not replace guidance from your healthcare provider. Cancer and treatment decisions are highly individual—always consult your physician or qualified healthcare professional regarding your specific situation.
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