Background: Chemoresistanceinvolving P-gp / MDR1 as uncertain factors affect the clinical response after the administration of neoadjuvant chemotherapy NAC) regimen Cyclophosphamid-Doxorubicin-5FU CDF). Response to chemotherapy can be assessed by changes in mRNA expression of MDR1 gene due to DNA damage in the cancer cell DNA synthesis by examination of quantitative Real Time PCR qRT-PCR). Objective: Knowing the direction of change in MDR1 mRNA expression before and after administration of NAC regimen CDF on Local advanced breast cancer LABC) based clinical response. Method: Longitudinal observation with cohort prospective design of 20 samples before and after NAC regimen CDF with assessing the expression of MDR1 mRNA in LABC by qRT-PCR examination. Expression MDR1 mRNA analysis by T test independent, paired T-test, Chi-Square Test. Results: qRT-PCRExamination of 20 samples pre and post NAC regimen CDF showed that a decline of MDR1 mRNA expression p <0.05. In the clinical response responsive decreased of MDR1 mRNA expression p<0.05 while nonresponsive decrease MDR1 mRNA p> 0.05. Increased of MDR1 mRNA expression in nonresponsive clinical response was 38.5% Conclusion: There was a decrease significantly of MDR1 mRNA expression both before and after NAC regimen CDF as well as on clinical response responsive MDR1 mRNA expression before NAC regimen CDF as a predictor of response to chemotherapy.
