Cancer treatment. What do we know at the present time about the effectiveness of selenium as an adjuvant treatment in cancer patients?
In a 2024 systematic review, researchers have evaluated the existing evidence from data from 12 studies with 2,483 adult patients undergoing cancer treatment. The types of cancer included non-Hodgkin lymphoma, head and neck cancer, thyroid cancer, acute myeloid or acute lymphocytic leukemia, stage I non-small lung cancer, breast cancer, cervical and endometrial cancer, prostate cancer, and non-invasive urothelial carcinoma [Krannich 2024].
The researchers’ analysis of the available data does not give a clear picture of the efficacy of selenium administration to adult cancer patients. One reason is that several of the evaluated studies did not report measurements of the patients’ serum selenium levels at the beginning or the end of the study. The studies that did report serum selenium levels used different ways to measure selenium levels. Moreover, the duration of the selenium administration and the type of selenium preparation and the dosage varied from study to study [Krannich 2024].
Selenium Deficiency versus Replete Selenium Status
The researchers point out that selenium supplementation has different effects, depending upon whether the selenium is administered to patients with deficiency levels or not. They cite evidence that selenium deficiency correlates with cancer, cardiovascular diseases, infertility, and a reduced immune response. Supplementation to maintain normal levels of selenium in the blood may prevent deficiency during cancer treatment [Krannich 2024].
But selenium supplementation of adults with optimal or replete selenium status will not bring further health benefits. For example, in patients undergoing radiation therapy, patients who had sufficient levels of selenium at baseline did not benefit from selenium supplementation. Radiation therapy patients with a deficiency of selenium at baseline did have significantly reduced toxicities on some scales [Krannich 2024].
Levels of Serum Selenium Status
To optimize the serum concentration of selenoprotein P, the serum selenium concentration must be in the range 120-130 mcg/L. To reach this level, the required selenium intake is at least 100 mcg per day. Selenoprotein P is the primary transporter of selenium in the blood circulation. It is also one of the major biomarkers of selenium status [Larsen 2024].
Depending on where one lives and what kind of diet one eats, achieving an appropriate daily intake level may require nutritional supplementation of 50 to 100 micrograms of selenium per day [Schomburg 2021; Winther 2020; Hurst 2010].
- Severely Deficient Status = less than 45 mcg/L
- Deficient Status = less than 70 mcg/L
- Sub-Optimal Status = 70 – 100 mcg/L
- Adequate/Replete Status = 100-120 mcg/L
- Optimal Status = 125-130 mcg/L
- Safe Upper Intake Level = 255 mcg/day
Key Findings in the 2024 Adjuvant Cancer Treatment Review
Selenium supplementation mitigates radiotherapy-associated dysphagia (difficulty swallowing).
Selenium supplementation is associated with significant reduction in chemotherapy-induced diarrhea.
Selenium supplementation reduces oral mucositis severity in leukemia patients – reduces inflammation and ulceration of the mucous membrane in the digestive tract.
Selenium supplementation decreases bone marrow suppression in cervical cancer treatment. Bone marrow suppression results in deficiencies of red blood cells, white blood cells, and platelets.
Selenium supplementation has no significant impact on the progression of prostate cancer.
Conclusion: Selenium as Adjuvant Cancer Treatment
The reviewed studies had methodical drawbacks. There are very few studies that provide a reliable answer to the question whether selenium supplementation can reduce the side effects of cancer treatment, raise the quality of life, or improve prognosis in adult cancer patients.
Regardless blood levels of selenium, no beneficial impact was found for overall survival, recurrence free intervals, progression free intervals, quality of life, and prostate-specific antigen levels compared to control/placebo groups.
If we want reliable results from selenium and cancer treatment studies, we need studies with larger group sizes, with cancer patients who have documented serum selenium deficiency, and with longer study durations.
Future studies must include measurements of serum selenium concentration and serum selenoprotein P concentration at the beginning and at the conclusion of the study.
Sources
EFSA. Scientific opinion on the tolerable upper intake level for selenium. EFSA J. 2023 Jan 20;21(1):e07704.
Hurst R et al. Establishing optimal selenium status: results of a randomized, double-blind, placebo-controlled trial. Am J Clin Nutr. 2010 Apr;91(4):923-31.
Krannich F et al. A systematic review of Selenium as a complementary treatment in cancer patients. Complement Ther Med. 2024 Nov;86:103095.
Larsen C et al. Selenium supplementation and placebo are equally effective in improving quality of life in patients with hypothyroidism. Eur Thyroid J. 2024 Jan 1:ETJ-23-0175.
Schomburg L. Selenium deficiency due to diet, pregnancy, severe illness, or covid-19-a preventable trigger for autoimmune disease. Int J Mol Sci. 2021 Aug 8;22(16):8532.
Winther KH et al. Selenium in thyroid disorders – essential knowledge for clinicians. Nat Rev Endocrinol. 2020 Mar;16(3):165-176.
The information presented in this review article is not intended as medical advice. It should not be used as such.