Sodium Selenite Supplementation in Patients With Head and Neck Cancer

Overview

The micronutrient selenium is an essential trace element in the human body. There are more than 25 proteins in the human body contain selenium, such as glutathione peroxidase and selenoprotein, which regulate the body's antioxidant and anti-inflammatory properties. Previous literatures had shown cancer patients have lower serum selenium concentrations than normal people, and lower serum selenium levels may be associated with increased cancer mortality. More than 50% of patients with locally advanced head and neck cancer are malnourished before treatment, and these patients often have deficiency of trace elements, including selenium. In these malnourished patients, they may have to endure increased treatment toxicity and treatment interruption when receiving standard concurrent chemoradiotherapy (CCRT). Interruption of treatment may lead to reduced therapeutic efficacy and compromised survival and recurrence rate. Several small studies have investigated whether oral administration of sodium selenite in patients with head and neck cancer undergoing radiation therapy can improve side effects and affect survival rates, but the results are inconsistent. Our study will use the intravenous form of sodium selenite (Zelnite®) to investigate the effect of selenium on the treatment outcomes of locally advanced head and neck cancer patients undergoing CCRT, such as therapy-related toxicities, quality of life, changes in selenium concentration in blood, nutritional, inflammation and immune markers, and tracking long-term survival and recurrence rates.

Selenium is an essential trace element for humans. It is involved in redox regulation, antioxidant functions, membrane integrity, and protection against DNA injury. In both animal models and human studies, it has been shown that selenium has cancer-protective effects and cytoprotective activities. Some mechanisms have been proposed to explain the anti-cancer effects of selenium, which include the antioxidant properties by selenoproteins, induction of conjugating enzymes that detoxify carcinogens, enhancement of the immune response, alterations in DNA methylation and blockage of the cell cycle to allow DNA repair. There has been conflicting response regarding selenium supplementation on the reduction of toxicity, antitumor efficacy and their quality of life in patients receiving radiotherapy. In the studies by Kiremidjian-Schumacher et al. and Elango et. al, sodium selenite supplementation was shown to significantly enhance cell-mediated immune responsiveness and improve defense systems in head and neck cancer patients. Micke et al. and Zimmerman et al. demonstrated the quality of life of patients suffering from head and neck cancer with lymphedema significantly improved after selenium supplementation. In the study by Büntzel et al., selenium supplementation reduced the radiation-associated side-effects of dysphagia developments in patients with head and neck cancer patients. However, some studies showed negative response of selenium supplementation in head and neck cancer patients. Weijl et al. showed oral selenium supplementation did not show improvement in cisplatin-induced toxicity or response rate in cancer patients. In the study by Mix et al., addition of oral selenium supplementation was well-tolerated but did not lower the incidence of severe mucositis or improve quality of life or survival outcomes in head and neck cancer patients undergoing concurrent chemoradiation (CRT). An early systematic review in Cochrane demonstrated there was still insufficient evidence to conclude efficacy of selenium in alleviating the side effects of chemotherapy or radiotherapy treatments. The aim of this study is to investigate the effect of intravenous selenium supplementation on the treatment outcome of head and neck patients undergoing CCRT (toxicities, quality of life, overall survival, progression-free survival), selenium concentration changes during CCRT, and its correlation with nutritional, inflammation and immune markers.