Principles of Chemotherapy - Experimental Oncology Graduate Study

Therapeutic Index• All anticancer drugs have normal tissue toxicity that limits the dose that canbe given.• If a drug is to be useful, its antitumor effects must occur at lower doses thanthose that cause dose-limiting normal-tissue toxicity.• Therapeutic index may bedefined as the ratio of the dosesrequired to produce a givenprobability of toxicity andantitumor effect.• E.g., the ratio of doses thatproduce a 5% probability ofsevere toxicity and 50%probability of antitumor effect.Source: IF Tannock and RP Hill, Basic Science ofOncology. 3 rd Ed., McGraw-Hill, 1998.4