The KRAS gene belongs to a class of genes known as oncogenes. When mutated, it has the potential to cause normal cells to become cancerous. KRAS tests are molecular diagnostic assays used to identify specific mutations in this gene within a tumor sample. These tests have become a standard of care in oncology, particularly for patients diagnosed with colorectal cancer, non-small cell lung cancer, and pancreatic cancer.

The primary clinical utility of KRAS testing is its role as a "predictive biomarker." For example, in metastatic colorectal cancer, patients with certain KRAS mutations are unlikely to respond to anti-EGFR (Epidermal Growth Factor Receptor) antibody therapies. By identifying these mutations beforehand, oncologists can avoid prescribing expensive and potentially toxic treatments that would be ineffective for that specific patient, instead opting for alternative therapeutic pathways. This is the essence of personalized medicine—matching the right treatment to the right patient based on their genetic profile.

With the recent development of drugs that specifically target certain KRAS mutations (such as KRAS G12C), the role of these tests has expanded from being purely "exclusionary" to being "inclusionary" for targeted therapy. As sequencing technologies like Next-Generation Sequencing (NGS) become more accessible, KRAS testing is being integrated into broader genomic panels, providing a more comprehensive view of the tumor's molecular landscape and guiding increasingly precise clinical interventions.