Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Chemoprotective drugs, such as dexrazoxane, may protect normal cells from the side effects of chemotherapy. Monoclonal antibodies such as trastuzumab can locate tumor cells and either kill them or deliver tumor-killing substances to them without harming normal cells. Radiation therapy uses high-energy x-rays to damage tumor cells. CTnT/cTnI/ANP/BNP were proved to be used as a biomarker of drug related cardiotoxicity. There are excellent correlations between the total cumulative dose of doxorubicin, the severity of the resulting cardiomyopathy, and the level of serum troponin-T.