en Biochimestry Biochimestry Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><em><span style="color:#0000ff;"><strong>Backgrounds:</strong></span></em> Chemotherapy for treatment of breast cancer uses some drugs to target and destroy the cancer cells. However, most of antineoplastic treatments are non-specific and the innate cells will be damaged. In this study, the effect of Adriamycin/Cytoxan (AC) chemotherapy on status of antioxidant enzymes and Se levels in breast cancer patients was evaluated.<br> <em><span style="color:#0000ff;"><strong>Methods:</strong></span></em> A prospective study, includes 50 breast cancer patients treated with AC chemotherapy (Adriamycin 60 mg/m², Cytoxan 600 mg/m²) from July 2016 until March 2017. First sampling was obtained before chemotherapy and the second, after 3 cycles of the intervention. Antioxidant enzyme activities (Catalase, Glutathione Peroxidase, Glutathione Reductase and Superoxide Dismutase) and Selenium (Se) levels in serum were measured by spectrophotometry and atomic absorption methods, respectively. Age, BMI, familial history, stage and grade of cancer, tumor site, type of surgery, Estrogen, Progesterone and HER2 receptors, were recorded from each patient. Paired-t test was employed for comparing the data before and after chemotherapy. Age and disease stages were compared by independent t-test.<br> <em><span style="color:#0000ff;"><strong>Results:</strong> </span></em>After 3 courses of chemotherapy, a significant decrease was observed in antioxidant enzymes and also Se (P<0.001). These studied indices were not significant in different age groups (&le;48, >48) and stages of disease (early, advanced).<br> <em><span style="color:#0000ff;"><strong>Conclusions:</strong></span></em> Our&nbsp;findings&nbsp;show&nbsp;that the AC chemotherapy in the breast cancer patients result in drastic changes in oxidant/antioxidant system of the body, specially reduction of Se levels and antioxidant enzymes activities. However, it seems that these changes are not necessarily dependent on the age and disease stage.</span></span> Breast cancer, Chemotherapy, Catalase, Glutathione Peroxidase, Glutathione Reductase, Superoxide Dismutase, Selenium. 403 409 http://caspjim.com/browse.php?a_code=A-10-71-6&slc_lang=en&sid=1 Fatemeh Pakmanesh fm.pakmanesh@gmail.com 100319475328460024927 100319475328460024927 No Student Research Committee, Babol University of Medical Sciences, Babol, Iran Daryoush Moslemi moslemi_d@yahoo.com 100319475328460024928 100319475328460024928 No Cancer Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Soleiman Mahjoub smahjoub20@gmail.com 100319475328460024929 100319475328460024929 Yes Cellular and Molecular Biology Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran