Genes that have genetical variation encode enzymes which metobolize drug, drug transporters, or drug targets. Variation in genes that can predict dose and safety of treatment for different types of cancer patient can have harmful influence on these patients’ treatment(25). For instance, polymorphism where in cytochrome P450 enzymes could cause to metabolite to drug slowly or very fast. So patient give an overdose symptoms or no response to drug by changing the pharmacokinetics of drug metabolism, also it may cause an adverse drug reaction(26). Thereby , forecasting optimal dose of drug , inducing the harmful side effects can be provided by using polymorphism(27). In familial breast cancer, patients shows low survival rate to treatment with tamoxifen that is chemotherapeutic drug because of genetic variation in CYP2D6 that is seen as a poor metabolizer (28). There are some studies abour genetic testing on drug label including test for CYP450 polymorphisms.

Prognosis

Insteaf of using clinicopathologic parameters as a biomarker in biochemical testing for prognosis and selection of therapatic way for cancer patient , Genotyping or gene expression profiling by microarray and protein analysis by mass spectrometry is used for prognostic biomarkers with the understanding of the molecular mechanism of cancer subtypes(29).

Biomarkers can be used alone or with combination of other parameters for classify subgroups according to their risk rate and for leading to therapy decision. For example, tissue microarray analysis with combining molecular and clinical biomarker is more efficient than the clasical clinical parameter for patient who has renal cell carcinoma(30).

Approaches and Tools for Personalized Medicine

Instead of using PCR, fluorescence in situ hybridization, immunohistochemistry, and sequencing for personalized medicine testing, high throughput analyses that consist of microarray, mass spectrometry, second generation sequencing, array comparative genomic hybridization, and high-throughput single nucleotide polymorphism (SNP) analysis were started to use after human genome project . These techniques can analyse numerous target at the same time(31). New technologies improve sesitiveness, speciality, trueness of new b