-Genetic biomarkers involve analyzing DNA or RNA for mutations, deletions, or other genetic alterations that may be associated with cancer. Examples include BRCA1 (BReast CAncer gene 1) and BRCA2 (BReast CAncer gene 2) mutations in breast and ovarian cancer, and mutations in EGFR common in lung cancer. Gene expression as well as their epigenetic modifications can serve as genetic biomarkers. Changes in DNA methylation patterns can be indicative of cancer, which rationalizes the use of methylation biomarkers. Hypermethylation of certain genes is associated with silencing tumor suppressor genes. -Cell-free DNA (cfDNA) / circulating tumor DNA (ctDNA) shed by cancer cells into the bloodstream can be analyzed for genetic mutations and alterations associated with specific cancers. -MicroRNA (miRNA) involved in gene regulation can be used as biomarkers since their expression profiles can be altered in cancer. -Metabolites -changes in metabolite profiles can indicate cancer-related alterations in metabolism, which rationalizes the use of metabolomic biomarkers. -Glycans are sugar molecules attached to proteins and lipids. Changes in glycosylation patterns on proteins and lipids can be associated with cancer and can serve as biomarkers. -Exosomes, small extracellular vesicles released by cells, can carry cancer-related molecules and are being investigated as potential biomarkers. -Imaging biomarkers for techniques like MRI, CT scans, and PET scans can reveal specific features associated with cancer, such as the size and location of tumors. PET scans use radioactive tracers to highlight areas with high metabolic activity, often indicating the presence of cancer. MRI can provide detailed images of soft tissues and is commonly used in cancer diagnosis. -Serologic markers can include antibodies and antigens that are detected in blood tests, such as the human papillomavirus (HPV) test for cervical cancer. Figure . General types of cancer biomarkers Cancer biomarkers can also be functionally classified into various types. The categories of biomarkers defined by the FDA-NIH Biomarker Working Group according to their clinical usage include: susceptibility and risk, diagnostic, monitoring, prognostic, predictive, pharmacodynamic and treatment response, and safety biomarkers. -Diagnostic (screening) biomarkers are used to detect and identify a given type of cancer in an individual. These markers are expected to have high specificity and sensitivity. -Prognostic biomarkers are used once the disease status has been established. These biomarkers are expected to predict the probable course of the disease including its recurrence, and they therefore have an important influence on the aggressiveness of therapy. -Predictive biomarkers serve to predict the response to a drug before treatment is started. This marker classifies the responsiveness of the individuals to a particular treatment. These biomarkers mainly arise from array-type experiments that make it possible to predict clinical outcome from the molecular characteristics of a patient's tumor. -Response biomarkers are used to show that a biological response, potentially beneficial or harmful, has occurred in an individual who has been exposed to a medical product or an environmental agent. -Monitoring biomarkers are measured repeatedly for assessing the status of a disease or medical condition or for evidence of a medical product's or an environmental agent's effect. -Susceptibility/Risk biomarkers indicate the potential for developing a disease or medical condition in an individual who does not currently have a clinically apparent disease or medical condition. -Safety biomarkers are measured before or after an exposure to a medical product or an environmental agent to indicate the chances or extent of toxicity as an adverse effect. The choice of biomarker(s) depends on the type of cancer being investigated and the specific diagnostic needs. Often, a combination of biomarkers and diagnostic methods is used to increase the accuracy of cancer diagnosis and staging. Additionally, ongoing research continues to uncover new biomarkers and refine existing ones, improving our ability to detect and diagnose cancer at earlier stages.