Genomic testing represents a significant advancement in modern cancer care, moving beyond simply identifying where a tumor is located. This technology focuses on the unique molecular blueprint of a patient’s cancer cells, revealing the specific changes in DNA and RNA that drive the tumor’s growth. Analyzing this genetic profile allows doctors to gain a deeper understanding of the disease. This enables more precise and personalized treatment strategies, shifting cancer management from a one-size-fits-all model to one based on the specific molecular alterations present in the tumor.
What Defines Genomic Testing
Genomic testing, often referred to as somatic testing, focuses on finding acquired genetic changes that exist only within the tumor cells. These alterations, known as somatic mutations, occur after conception as the cancer develops over time. Analyzing the tumor’s DNA and RNA provides a molecular profile that explains how the cancer behaves and grows.
This differs from standard genetic testing, called germline testing, which looks for inherited DNA changes present in all cells from birth. Germline mutations, such as those in the BRCA1 and BRCA2 genes, indicate a hereditary predisposition to cancer that can affect family members. Genomic testing, by contrast, seeks actionable targets for therapy directly within the cancer itself.
The goal of genomic testing is to analyze a wide panel of genes to identify alterations such as single-nucleotide variants, gene fusions, and copy number changes unique to the tumor. This comprehensive analysis allows oncologists to understand the specific molecular pathways that are malfunctioning and supporting the cancer. The resulting molecular profile provides the information needed to select treatments designed to interact with these tumor characteristics.
How the Testing Process Works
The process of genomic testing begins with obtaining the biological material that contains the tumor’s genetic information. The most common method involves using a tissue sample collected during a prior biopsy or surgical procedure. This solid tumor tissue is sent to a specialized laboratory where the DNA and RNA are extracted from the cancer cells.
An increasingly common and less invasive method is the liquid biopsy, which involves a simple blood draw. This blood sample is analyzed for circulating tumor DNA (ctDNA), which are fragments of the tumor’s genetic material shed into the bloodstream. This method is useful when a tissue biopsy is not feasible or when monitoring the cancer’s response to treatment over time.
Once the tumor’s genetic material is isolated, the lab employs Next-Generation Sequencing (NGS) to read the DNA and RNA code. NGS works by first breaking the genetic material into millions of small fragments. Specialized machines then read the sequence of building blocks, or bases, in each fragment simultaneously.
A powerful computer then reassembles these millions of short sequences like a complex puzzle and compares the resulting tumor code against a reference human genome. This comparison highlights any deviations or mutations present in the tumor sample. The sequencing process can analyze hundreds of genes at once, providing a comprehensive report of the tumor’s molecular changes.
Using Genomics to Guide Treatment
The primary purpose of genomic testing is to enable precision medicine by matching a patient’s tumor profile to the most effective treatment options. By identifying a specific genomic alteration, doctors can select a targeted therapy designed to attack that molecular change. For example, finding a mutation in the EGFR gene in lung cancer or a BRAF mutation in melanoma can indicate that a patient will respond well to a drug that blocks the activity of that altered protein.
This approach is a step away from traditional chemotherapy, which broadly kills all rapidly dividing cells, often leading to severe side effects. Targeted therapies, such as tyrosine kinase inhibitors or PARP inhibitors, are designed to be more selective, causing less damage to healthy cells. Genomic results may also predict a tumor’s likely response to immunotherapy by revealing biomarkers like Tumor Mutational Burden (TMB) or Microsatellite Instability (MSI).
Genomic profiling is also valuable for determining eligibility for clinical trials, which often seek patients with specific molecular alterations. If a patient’s tumor harbors a change for which no approved drug exists, the genomic test can connect them to a trial studying a novel targeted agent. The molecular profile also provides prognostic information, offering insight into the potential behavior of the disease and helping to monitor for signs of treatment resistance.
Interpreting Test Results
The results of genomic testing are compiled into a detailed report that the oncologist must translate into a clear treatment plan. The findings are categorized to distinguish between alterations that have immediate clinical significance and those that do not. The most important findings are “actionable mutations,” which are genetic changes for which an FDA-approved drug or a clinical trial option exists.
However, a significant portion of the report may list findings known as Variants of Uncertain Significance (VUS). A VUS is a genetic change whose association with cancer growth or drug response has not yet been established by scientific evidence. Clinicians should not use a VUS result as the sole basis for making a treatment decision until more data becomes available.
To address the complexity of these technical reports, many institutions utilize a multidisciplinary Molecular Tumor Board. This board, composed of oncologists, molecular pathologists, and genetic specialists, reviews the data and discusses the most appropriate treatment recommendations. They interpret the results within the context of the patient’s overall disease, translating the specialized data into clinical action.
Sometimes the report may not find any actionable mutations for which a targeted drug is currently available. Even in this scenario, the information is valuable because it can prevent the use of expensive or ineffective targeted therapies. The goal of interpreting these results is to ensure that every patient receives the most informed, personalized, and evidence-based treatment strategy possible.