A systematic review of Selenium as a complementary treatment in cancer patients

Background

Selenium, a trace element with antioxidant properties, has been widely studied for its benefits in cancer treatment. This systematic review aims to critically evaluate existing evidence on the effectiveness of selenium as a complementary treatment in cancer patients.

Method

In May 2023, a systematic search was conducted searching five electronic databases (Embase, Cochrane, PsychInfo, CINAHL and Medline) to find studies concerning the use, effectiveness and potential harm of selenium substitution therapy on adult cancer patients undergoing cancer treatment. Including and excluding patient criteria were defined beforehand.

Results

From 4511 search results, 12 studies in 14 publications with 2483 patients were included in this systematic review. Types of cancer covered in the reviewed studies are non-Hodgkin lymphoma, head and neck cancer, thyroid cancer, acute myeloid or acute lymphocytic leukaemia, stage I non-small lung cancer, breast cancer, cervical and endometrial cancer, prostate cancer and non-invasive urothelial carcinoma. Common outcomes were PSA change, radiotherapy associated toxicities, overall survival (OS), recurrence free interval (RFI) and quality of life (QoL). Most studies showed some concerns in the risk of bias evaluation. The results were heterogeneous: Regarding radiotherapy toxicities, patients with sufficient levels of Se at baseline do not profit of Se supplementation, while those with a deficiency of Se at baseline have significantly reduced toxicities on some scales. Regardless blood levels of Se, no benefit was found for OS, Recurrence Free Interval, Progression Free Interval, Quality of life and PSA compared to control/placebo group.

Conclusion

Due to the very heterogeneous results and methodical limitations of the included studies, a clear statement regarding the effectiveness of Se supplementation is not possible, whereas cancer patients with a Se deficiency could profit from a Se supplementation during radio- or chemotherapy. Further studies should define Se deficiency as inclusion criterion and analyze levels of Se during time of intervention.