Cancer biomarkers are biological molecules found in blood, other body fluids, or tissues that indicate the presence of cancer. They can be proteins, genes, or other substances produced by cancer cells or by the body in response to cancer. These markers help in diagnosing cancer, predicting its progression, and monitoring treatment effectiveness. Researchers use cancer biomarkers to develop targeted therapies and personalized medicine approaches. By understanding specific biomarkers associated with different types of cancer, such as breast cancer or lung cancer, doctors can tailor treatments to individual patients, improving outcomes and minimizing side effects.