The essential
trace element selenium, which is a crucial cofactor in the most important endogenous antioxidative systems of the human body, is attracting more and more the attention of both laypersons and expert groups. The interest of oncologists mainly focuses in the following clinical aspects: radioprotection of normal tissues, radiosensitizing in malignant
tumors, antiedematous effect, prognostic impact of
selenium, and effects in primary and secondary
cancer prevention.
Selenium is a constituent of the small group of
selenocysteine-containing
selenoproteins and elicits important structural and enzymatic functions.
Selenium deficiency has been linked to increased
infection risk and adverse mood states. It has been shown to possess
cancer-preventive and cytoprotective activities in both animal models and humans. It is well established that Se has a key role in redox regulation and
antioxidant function, and hence in membrane integrity, energy metabolism and protection against DNA damage. Recent clinical trials have shown the importance of
selenium in clinical oncology. Our own clinical study involving 48 patients suggest that
selenium has a positive effect on radiation-associated secondary
lymphedema in patients with limb edemas, as well as in the head and neck region, including endolaryngeal
edema. Another randomized phase III study of our group was performed to examine the cytoprotective properties of
selenium in radiation oncology. The aim was to evaluate whether
sodium selenite is able to compensate a preexisting
selenium deficiency and to prevent radiation induced
diarrhea in
adjuvant radiotherapy for pelvic gynecologic
malignancies. Through this study, the significant benefits of
sodium selenite supplementation with regards to
selenium deficiency and
radiotherapy induced
diarrhea in patients with cervical and
uterine cancer has been shown for the first time in a prospective randomized trial. Survival data imply that supplementation with
selenium does not interfere with the positive
biological effects of
radiation treatment and might constitute a valuable adjuvant
therapy option especially in marginally supplied individuals. More recently there were emerging concerns coming up from two large clinical prevention trials (NPC, SELECT), that
selenium increases the possible risk of developing diabetes type II. Despite obvious flaws of both studies and good counterarguments, a controversial debate remains on the possible advantage and risks of
selenium in
cancer prevention. However, in the light of the recent clinical trials the potential benefits of
selenium supplementation in
tumor patients are undeniable, even if further research is needed.