Multidrug resistance in non-small-cell lung cancer

Resistance to cytotoxic drugs is an important cause of treatment failure. T he causes are complex and may be determined by a combination of the tumour characteristics, such as the proportion of resting cells, adequacy of blood supply, and specific cellular mechanisms, as in the multidrug resistance p henotype. In lung cancer four types of multidrug resistance have been defin ed on the basis of the cellular drug targets involved, i.e., classical mult idrug resistance (MDR), non-P-glycoprotein MDR (also called MRP), atypical MDR (mediated through altered expression of topoisomerases II) and lung res istance-related protein. In lung cancer the role of the different forms of multidrug resistance is complex and only partially understood.