RESUMO
Background: Zinc deficiency during long-term chemotherapy and its related symptoms, including skin rash, taste disorders, and oral mucositis, have not been sufficiently investigated. Methods: This prospective observational study enrolled patients with gastric and colorectal cancer who underwent standard first-line chemotherapy. According to the Practice Guidelines for Zinc Deficiency, zinc deficiency is defined as a serum level of <60 µg/dL. Serum zinc levels were measured before and after (1, 3, and 6 months) chemotherapy, and symptoms were assessed using the Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events version 1.0. Repeated measures were analyzed using a generalized linear mixed model. Results: Of the 61 enrolled patients, 48 who underwent standard first-line chemotherapy with fluoropyrimidine plus oxaliplatin were analyzed. Zinc deficiency was observed in 18 patients (38%) before chemotherapy. The least-squares means of serum zinc levels significantly decreased at 3 and 6 months of chemotherapy in 30 patients without zinc deficiency at the start of chemotherapy (both P<0.01) but not in 18 with zinc deficiency at the beginning. Changes in serum zinc levels during chemotherapy negatively correlated with changes in taste, rash, and itching (all P<0.04) in patients without zinc deficiency before treatment initiation. Conclusions: Serum zinc levels decreased during chemotherapy in zinc-non-deficient patients at the beginning of chemotherapy and correlated with taste changes, skin rash, and itching. Therefore, investigating whether zinc supplementation ameliorates these symptoms is necessary.