Efficacy and Interaction of Antioxidant Supplements as Adjuvant Therapy in Cancer Treatment

Abstract

Oxidative stress is a key component in carcinogenesis. Although radiation produces reactive oxygen species, some anticancer agents such as alkylating agents, platinum and antitumor antibiotics exert cytotoxicity by generating free radicals. Nonenzymatic exogenous antioxidants such as vitamins, minerals, and polyphenols can quench ROS activity. However, whether antioxidants alter antitumor effects during radiotherapy and some types of chemotherapy remains unclear. In the present study, we reviewed antioxidants as an adjuvant therapy for cancer patients during chemotherapy or radiotherapy. Electronic literature searches were performed to select all randomized controlled clinical trials (RCTs) in which antioxidants were administered to cancer patients along with chemotherapy or radiotherapy. Articles or abstracts written in English were included. In total, 399 reports received primary screening. Duplicated articles and those meeting the exclusion criteria (not RCT, not human, and no oral administration) were excluded. Finally, 49 reports matching the inclusion criteria were included. It was difficult to determine whether antioxidants affect treatment outcomes or whether antioxidants ameliorate adverse effects induced by chemotherapy and radiotherapy. It is desirable to use an evidence-based method to select supplements best suited to cancer patients. Although there are many opinions about risks or benefits of antioxidant supplementation, we could mostly conclude that the harm caused by antioxidant supplementation remains unclear for patients during cancer therapy, except for smokers undergoing radiotherapy.

Milk Thistle (Silybum Marianum) as a Supportive Phytotherapeutic Agent in Oncology

“…Obecně se podávání antioxidantů při léčbě onkologického onemocnění nedoporučuje, a to kvůli možnému snížení účinků léčby, která je často založená na tvorbě volných radikálů [54]. Ve výše uvedené studii na myších zabývající se poškozením plic radiací se porovnával také vliv samotné radiace a radiace v kombinaci se silymarinem na nádor plic, jehož vznik in vivo byl podmíněn chemicky.…”

Cancer, Oxidative Stress, and Metastasis

“…A systematic review found no benefit of supplemental ascorbate (vitamin C) for overall or progression-free survival in cancer patients, most of whom had breast or colorectal cancer (Jacobs et al 2015). Another systematic review examined treatment efficacy and patient survival with the use of any adjuvant antioxidants during chemotherapy or radiotherapy (Yasueda et al 2016). The trials showed contradictory results, but …”

Antioxidant and cytotoxic properties of novel spirocyclic benzothiazolines

“…Antioxidants are also thought to be beneficial in alleviating the adverse effects of chemotherapy and/or radiotherapy [7]. However, the precise mechanism(s) of action of antioxidants in cancer is not yet fully known and clinical trials have still been reporting inconsistent outcomes [1,[4][5][6][7][8][9].…”