Polymorphisms of genes encoding drug transporters or cytochrome P450 enzymes and association with clinical response in cancer patients: a systematic review.

The controversial results may be due to several factors including difference in populations studied, sample size, tumor sites and stages, chemotherapeutic drug regimens, and evaluation parameters for efficacy and/or toxicity. Before the information can be successfully applied to individualized cancer chemotherapy, further studies should be focused on these promising genetic markers and their association with clinical outcomes using standardized protocols.