Chemotherapy resistance refers to the phenomenon where cancer cells become less susceptible to the effects of chemotherapeutic drugs, leading to a reduced treatment efficacy and ultimately, treatment failure. This resistance can occur through various mechanisms, including genetic mutations, altered drug metabolism, and enhanced DNA repair mechanisms in cancer cells. Understanding and overcoming chemotherapy resistance is a critical area of research in oncology, as it has significant implications for improving cancer treatment outcomes and patient survival. Researchers are exploring strategies such as combination therapies, targeted therapies, and immunotherapies to overcome or prevent chemotherapy resistance in cancer patients.