Genomic cancer treatment changes how the disease is managed. Instead of classifying cancer by its location, such as the lung or colon, this approach focuses on the specific genetic characteristics of a patient’s tumor. Every cancer has a unique genetic fingerprint composed of DNA alterations that control its growth. By identifying these unique drivers, therapies can be chosen to target the distinct molecular vulnerabilities of the cancer cells.
This shift in perspective means a tumor in the breast might be treated similarly to one in the lung if they share the same genetic mutation. The treatment is matched directly to the tumor’s biological instructions for more effective outcomes. This strategy does not apply to every patient but offers a powerful alternative for many.
The Process of Genomic Profiling
Genomic cancer therapy begins with obtaining a sample of the tumor’s genetic material. The most common method is a biopsy, where a small piece of tumor tissue is surgically removed. The sample is sent to a lab where DNA is extracted from the cancer cells to prepare it for sequencing.
Once extracted, the tumor’s DNA undergoes an analysis known as genomic sequencing or tumor profiling. This process scans the cancer’s genetic code to find mutations that are not present in the patient’s normal cells. This analysis creates a detailed map of the genetic abnormalities driving the tumor’s growth and survival.
A liquid biopsy is an alternative to a tissue biopsy. This blood test analyzes tumor DNA fragments that have been shed into the bloodstream. This method is less invasive and can be useful for monitoring the cancer’s evolution over time.
Types of Genomic-Guided Therapies
Genomic profiling informs several advanced treatment strategies. One primary strategy is targeted therapy, which uses drugs to interfere with specific molecules involved in cancer growth. These targets are often the proteins created by the mutated genes identified during sequencing. These drugs are more precise than chemotherapy, acting like a key in a specific lock to block the signals that tell cancer cells to multiply.
Genomic information also helps determine if a patient could benefit from immunotherapy. These treatments help the body’s immune system attack cancer cells, and certain genomic markers can predict a strong response. For example, a high tumor mutational burden (TMB) indicates the tumor has many mutations, making it more susceptible to an immune attack. The microsatellite instability-high (MSI-H) marker serves a similar purpose.
Pharmacogenomics uses a patient’s genetic information to predict their response to drugs, including conventional chemotherapies. By understanding how a person’s genetics influences drug metabolism, doctors can select effective agents, tailor dosages, and avoid treatments likely to cause severe side effects. This makes the therapy safer and more personalized.
Cancers Commonly Treated with Genomic Approaches
Genomic-guided therapies are standard for several cancers with common, targetable mutations. In non-small cell lung cancer, for instance, many tumors are driven by mutations in genes such as EGFR, ALK, and ROS1. Patients with these alterations can be treated with oral medications that block the mutated genes, often leading to better outcomes than chemotherapy.
Genomics has also impacted breast cancer treatment. The identification of HER2-positive breast cancer, where tumors have an overactive HER2 gene, led to therapies that target the HER2 protein. Additionally, inherited mutations in the BRCA1 and BRCA2 genes increase the risk of developing breast and ovarian cancers and can be targeted with drugs known as PARP inhibitors.
This approach is also used in other cancers. In melanoma, a large portion of patients have a mutation in the BRAF gene, for which specific inhibitor drugs have been developed. For colorectal cancer, identifying mutations in the KRAS gene is routine, as its presence can predict a lack of response to certain targeted therapies, guiding doctors away from ineffective treatments.
Limitations and Access to Genomic Testing
Genomic profiling has limitations. Testing does not always reveal an “actionable” mutation, which means a tumor may not have a known genetic weakness that can be treated with an existing targeted drug. In these cases, the patient is left with standard treatment options.
Tumor heterogeneity and evolution present another challenge. A single tumor can be composed of cell populations with different genetic mutations. A therapy targeting one mutation may kill one subpopulation of cells, but others may survive and continue to grow. Over time, cancers can also develop new mutations that make them resistant to a previously effective therapy.
Practical barriers also limit access. Comprehensive genomic testing is complex and may not be available at all cancer treatment centers. The cost of testing and targeted therapies can be substantial, and insurance coverage varies, creating financial challenges for patients.