Selenium for alleviating the side effects of chemotherapy, radiotherapy and surgery in cancer patients

Abstract

Background: This is an updated version of the original Cochrane review published in Issue 3, 2006. Selenium supplements are frequently used by cancer patients. Selenium is an essential trace element and is involved in antioxidant protection and the redox-regulation in humans. Several adverse effects of radiotherapy and chemotherapy in cancer patients as well as cellular processes that maintain chronic lymphoedema have been linked to oxidative cell processes in the human body. Selenium has been claimed to alleviate side effects of conventional cancer therapy and recently been investigated as a remedy against chemotherapy and radiotherapy-associated side effects and secondary lymphoedema. Objectives: This review assessed the effects of supplementary selenium on adverse effects of conventional radiotherapy, chemotherapy, or surgery in oncology patients and on quality of life/performance status during and after oncological treatment. Search methods: The Cochrane Pain, Palliative & Supportive Care Trials Register, the Cochrane Database of Systematic Reviews, the Database of Abstracts of Reviews of Effects (DARE), CENTRAL, MEDLINE, EMBASE, SIGLE, Cancerlit, CCMed, the German online register for cancer trials, the ISRCTN, the mRCT, the NCI Clinical Trials register databases were searched and most updated in July 2007. Selection criteria: Randomised controlled trials (RCTs) of selenium mono-supplements in cancer patients undergoing tumour specific therapy, such as chemotherapy, radiotherapy or surgery. Data collection and analysis: Two review authors independently checked trials for eligibility, extracted data and assessed trial quality. Main results: One new included study as well as further participants to a study already included was added to this update involving a further 39 participants. There were a total of three studies included involving 162 participants for this update. For this review two RCTs were included investigating secondary lymphoedema in 60 women after breast cancer surgery and 20 men and women after head and neck cancer surgery. One ongoing trial with preliminary results of 82 participants was also identified studying radiotherapy induced diarrhoea as a secondary outcome. All studies had considerable drawbacks with regards to quality and reporting. One study on secondary lymphoedema reported a decreased number of recurrent erysipela infections in the selenium supplementation group compared to placebo. The second study reported a decreased facial swelling in the selenium group in a two-week period following surgical tumour resection. However, results must be interpreted with caution and cannot be generalised to other populations. The ongoing trial on radiotherapy associated diarrhoea preliminarily reported a lower incidence of diarrhoea in participants receiving selenium supplementation concomitant to pelvic radiation, however, no data were presented. We must await publication of final results to discuss these findings in detail. No RCTs were found studying the effect of selenium supplementation on other therapy-associated toxicities or quality of life/performance status in cancer patients. Authors' conclusions: There is insufficient evidence at present that selenium supplementation alleviates the side effects of tumour specific chemotherapy or radiotherapy treatments or that it improves the after-effects of surgery, or improves quality-of-life in cancer patients or reduces secondary lymphoedema. To date, research findings do not provide a basis for any recommendation in favour or against selenium supplementation in cancer patients. Potential hazards of supplementing a trace mineral should be kept in mind. Since the last version of this review, the one new additional study has not provided information to change the conclusions of the original review.