Utility of Circulating Tumor DNA-Based Liquid Biopsies in Patients with Cancer Receiving Immunotherapy

Liquid biopsies offer a promising, noninvasive approach for monitoring and predicting responses to immunotherapy across multiple solid tumors. For the most part these are circulating tumor DNA (ctDNA) based assays. Here, we discuss the biological basis, clinical evidence, and potential applications of different types of ctDNA assays in tracking tumor dynamics, distinguishing pseudoprogression, and assessing minimal residual disease. We explore the current limitations, assay variability, and future directions, including integration with other biomarkers and real-world clinical trials aimed at validating ctDNA as a routine tool in precision immuno-oncology.