The comprehensive review of liquid biopsy as a cutting-edge, non-invasive technique for cancer detection, diagnosis, and monitoring may be found in the document “Liquid Biopsy in Cancer Diagnosis – Treatment Methodology and Applications.” Via liquid biopsy, tumor-related indicators present in physiological fluids such as blood, urine, and saliva are examined, including exosomes, circulating tumor cells (CTCs), and circulating tumor DNA (ctDNA). Liquid biopsy enables regular, real-time sampling of tumor dynamics, in contrast to standard tissue biopsies, which are invasive and restricted to particular tumor regions. This renders it a potent instrument for the identification of cancer mutations and the tracking of tumor progression, particularly in cases of metastatic or elusive cancers. Technological developments like digital droplet PCR (ddPCR) and next-generation sequencing (NGS) have greatly improved the sensitivity and precision of ctDNA detection, making it possible to identify unusualexceptionally rare genetic mutations. This enhances the efficacy of tailored cancer treatment and monitoring. The genetic heterogeneity of cancers is captured by liquid biopsies, providing information on several tumor subclones that may be missed by traditional biopsies. The document also describes the use of different body fluids for different forms of cancer, such as head and neck and urological tumors, such as saliva, urine, and blood. Blood is the most often utilized medium for tracking genetic changes due to its ease of accessibility. Saliva and urine are useful in the detection of head and neck malignancies and bladder cancer, respectively. Liquid biopsy has several advantages, but it also has drawbacks, such as the requirement for standardized procedures, high prices, and differences in sensitivity and specificity between platforms.In order to overcome these obstacles and integrate liquid biopsy into standard clinical practice, the paper emphasizes the significance of more research and development. This will improve patient outcomes, early cancer detection, and personalized treatment.