In the treatment of cancer, a narrow therapeutic window generally exists between toxicity and suboptimal therapy. In addition, interindividual variation in drug metabolism seriously complicates therapy. Genetic polymorphisms in phase 1 and phase 2 enzymes are present in the population and may explain part of the observed interindividual variation in drug pharmacokinetics. For the cytochrome P450 superfamily, information on variant alleles encoding enzymes with decreased activity is rapidly on the increase. The potential of applying pharmacogenetic screening before therapy in the treatment of cancer seems to be greatest for CYP2B6 (cyclophosphamide treatment), CYP2C8 (paclitaxel therapy), and CYP3A5; however, the drugs of interest still need to be identified for this latter enzyme.

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Therapeutic Drug Monitoring
Department of Clinical Chemistry

van Schaik, R.H.N. (2004). Implications of Cytochrome P450 Genetic Polymorphisms on the Toxicity of Antitumor Agents. In Therapeutic Drug Monitoring (Vol. 26, pp. 236–240). doi:10.1097/00007691-200404000-00027