Cancer is a public health problem worldwide, with an estimated of 27 million new cases and 17 million cancer deaths in 2030. In Brazil, estimates for cancer in 2014, indicate the occurrence of approximately 580 000 new cases. Fluoropyrimidines are used in the main chemotherapy regimens targeted to tumors of the gastrointestinal tract. Recently, much has been investigated on causes of different individual responses to chemotherapy.Thus, it has been sought an individualized therapy that can maximize drug efficacy and minimize adverse effects associated with drugs. We aimed to seek the association of an INDEL polymorphism (rs16430) in TYMS gene with the pattern of response to chemotherapy drugs based on fluoropyrimidines, in order to contribute to the development of personalized medicine. We studied 151 samples of cancer patients treated with fluoropyrimidine, from a population of the Brazilian Amazon region with high interethnic admixture. An INDEL polymorphism (rs16430) was genotyped in TYMS gene that is involved in the response to treatment using fluoropyrimidines. The research reported that most patients had advanced disease at diagnosis, of which 32.7% were treated with palliative intent, and 22.8% neoadjuvant treatment. Our results show that the INDEL polymorphism in the TYMS gene appears to have a protective effect on tumor progression (p = 0.033). Patients treated with fluoropyrimidine who were wild homozygous (INS / INS) had a 24% protection to tumor progression compared to other genotypes of this polymorphism. Estimates of global genetic ancestry of the sample investigated were: 62.4% European, 25.2% Amerindian and 12.4% African. It was possible to establish an inverse correlation between the increase of Amerindian ancestry and metastasis (p = 0.024). Pharmacogenetic studies can provide a personalized therapy toxicity reducing mortality and improving therapeutic efficacy, thereby providing a cancer therapy with better clinical results.
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