[Drug administration in combination for management of cancer]

The use of drugs in combination for the management of cancer patients aims at the increased therapeutic advantage by elimination the problem of the heterogeneous sensitivity of cancer cells to anticancer drugs, and by delaying or preventing the development of drug resistance within given tumors. Theoretically, the effects of drugs in combination are classified as antagonistic, subadditive, additive and synergistic. Since these results hold for both tumors and hosts, the effects of combined drugs should be considered in terms of therapeutic index. From this viewpoint, the choice and administration schedule of drugs in combination must be synergistic or additive for the tumors and antagonistic or subadditive for the hosts in regard to combined effects. Thus, the rationale for combined drug therapy should be considered from the aspects of biochemical basis, drug resistance, cytokinetic and pharmacologic rationales, and toxicologic basis.