chemosensitivity

Chemosensitivity refers to the degree to which cells, tissues, or organisms respond to chemical agents, particularly cytotoxic drugs used in chemotherapy. In clinical oncology, chemosensitivity denotes how susceptible a tumor is to a given chemotherapy regimen. The concept also applies to microbes and other cells in toxicology and antimicrobial susceptibility testing.

Determinants include intrinsic cellular factors such as drug uptake and efflux (transporters), metabolic activation or inactivation, DNA repair capacity, apoptosis pathways, and cell cycle dynamics; microenvironmental factors like hypoxia, pH, and stromal interactions; and genetic alterations that influence drug targets or resistance mechanisms. Tumor heterogeneity and evolution under treatment can create mixed populations with varying chemosensitivity.

Assessment methods include in vitro chemosensitivity assays that measure cell viability after drug exposure, ex vivo testing on patient tumor samples, pharmacogenomic profiling, and functional assays. These are used to guide therapy in some settings, particularly in personalized medicine, but their predictive value is variable and not universally reliable due to factors such as tumor microenvironment and assay limitations.

Clinical use and challenges: while chemosensitivity testing can help identify effective agents and minimize toxicity, standardization, cost, and turnaround time limit routine use in many cancers. Resistance can emerge through multiple mechanisms, necessitating combination therapies and adaptive treatment strategies. Ongoing research aims to improve predictive models by integrating genomics, transcriptomics, and functional assays.