This treatment at high doses has a prooxidant action, indicated in cancers. Vitamin C increases the cytotoxic efficacy of chemotherapy and radiotherapy treatments. It reduces mitochondrial stress. Reduces DNA damage. Reduces ATP depletion. Increases collagen production. Reduces hypoxia, thus reducing tumor viability. Reduces tissue inflammation by modulation of the enzyme kinase. It is immunomodulatory. Vitamin C is a safe and effective treatment for cancer patients undergoing chemotherapy and/or radiotherapy.