Zinc Supplementation on Markers of Oxidative Stress in Post Operative Colorectal Cancer During Chemotherapy Cycles

Objective: To determine the oxidative stress during cycles of chemotherapy in patients after surgery for colorectal cancer, with or without oral zinc supplementation. Subjects: Twenty four adults from both genders participated in this study. All patients underwent stage II, III or IV colorectal cancer surgical resection and were starting chemotherapy in HCFMRP- USP. Patients were randomized into two groups. The first one (QTx-Zn Group, n=10) received 70 mg/d of zinc orally and the second one received placebo (QTx-Placebo Group, n=14) for 16 weeks. The study also included 30 healthy volunteers matched for age, gender and socioeconomic status, who received 70 mg/d of zinc supplement (Control-Zn Group, n=21) or placebo (Control-Placebo Group, n=9) for 16 weeks. Methods: The questionnaires about dietary intake (semiquantitative food frequency and food record), fatigue and quality of life (FACIT-F) and questionnaires that assess the side effects of chemotherapy (CTCAE) were evaluated. Anthropometry and bioelectrical impedance measurements were made. Blood collection was performed before the 1st, 2nd, 3rd and 4th cycles of chemotherapy (median duration of 21 days among cicles). Routine laboratory tests, vitamin E and markers anti and pro-oxidants (MDA, SOD, GPx and isoprostane) ere determined. The control group underwent the same procedures, except for chemotherapy. A longitudinal linear mixed effects model was adjusted for each of the variables of interest. The models were fitted using PROC MIXED of SAS version 9 (SAS, CARY, NC, USA). To analyze the association of categorical variables in the different items of the CTCAE, the investigators used the Fisher exact test. Results: The oral zinc supplementation was sufficient to increase plasma levels of zinc and did not alter food intake, body composition and routine laboratory evaluation of patients undergoing chemotherapy for colorectal cancer. Compared with QTx-Placebo Group, QTx-Zn Group showed lower prevalence of complai