Genetic testing and biomarker analysis have become integral to modern oncology, guiding risk assessment, diagnosis, and therapy selection. Genetic profiling identifies mutations and gene expressions linked to specific cancers, enabling personalized treatment strategies. Biomarkers, such as HER2 in breast cancer and EGFR in lung cancer, inform targeted therapies, improving efficacy and reducing side effects. Liquid biopsies, a non-invasive approach, complement tissue-based testing by detecting circulating tumor DNA and RNA. Advances in bioinformatics and AI-driven analysis enhance the interpretation of complex genetic data. As research progresses, genetic testing is expected to play a larger role in early detection and preventive oncology.