Yet another study showing how selenium status impacts cancer risk. This one is serum selenium and laryngeal cancer. Observational studies have reported an inverse relationship between selenium status (blood or toenail) and the risk of laryngeal cancer; however, the impact of low serum selenium level on survival has not been evaluated. The goal of this current study, Serum selenium levels and the risk of progression of laryngeal cancer, was to evaluate whether circulating selenium levels at time of diagnosis was associated with outcome among a cohort of laryngeal cancer patients residing in Szczecin, Poland.
Cypress Systems requested insight from Jim Roufs, RD, MS, our colleague and industry product formulator. Below is his analysis of the study as it relates to significance and support for selenium as a means to reduce laryngeal cancer risk.
- Study was conducted in Poland, which is known to be selenium deficient as well as the rest of Europe.
- The larynx is also known as the voice box, since it is involved in making sound, but it is also involved in respiration as well as protecting food from going down the trachea.
- Laryngeal cancer has poor survival rates with surgery as the primary treatment.
- Adjuvant treatment includes radiotherapy and chemotherapy, but is primarily employed to achieve local control and have little impact on survival.
This prospective study, of 296 patients diagnosed with laryngeal cancer in Szczecin, Poland, measured serum selenium levels at diagnosis and prior to treatment. Patients were followed from the date of diagnosis to death at five years. Vital status was obtained by linkage to the Polish National Death Registry.
Study subgroups and selenium serum levels
Key findings:1. Five-year survival was directly and positively related to serum selenium levels; ie, the higher the serum selenium levels at diagnosis, the greater the chance that the person will still be alive 5 yrs later (p<0.0001).
Probability of Survival Years after Diagnosis
2. More specifically, compared to those with the highest levels of serum selenium (ie, the upper quartile or quartile 4, with serum Se levels of 66.8-103.1μg/l), who had a 5 yr survival rate of 82.0%;
- Quartile 3 (58.0-66.2 μg/l) had a 5 yr survival rate of 4%
- Quartile 2 (50.1-57.9 μg/l) 0%
- Quartile 1 (ie, those with the lowest serum Se; 30.3-50 μg/l) 6%
3. Conversely, the risk of dying is directly and inversely related to serum Se levels (ie, compared to those in the upper quartile or quartile 4, with serum Se levels of 66.8-103.1μg/l), the age- and sex-adjusted Hazard Ratio (HR; ie, the risk of dying from any disease within 5 yrs when adjusted for age and sex; p<0.0001) were as follows:
- Quartile 3 – HR 15
- Quartile 2 – HR 95
- Quartile 1 – HR 01 (it is worth noting that although men comprised 86% of the 296 subjects involved in this study, the HR ratio for men was 6.5 (p<0.0001), where it was 13.2 for women (p=0.02).
Hazard ratios, 95% confidence intervals for factors on survival from laryngeal cancer.
4. Conversely, the risk of dying is directly and inversely related to serum Se levels (ie, compared to those with the highest serum levels), even when age, sex, stage of cancer, radiotherapy, chemotherapy and surgery were all taken into account [ie, the Fully-adjusted or multivariate Hazard Ratio (HR); p<0.0001, were as follows]:
- Quartile 3 – HR 51
- Quartile 2 – HR 01
- Quartile 1 – HR 07
Age- and sex-adjusted hazard ratios and 95% confidence intervals for low (quartile 1) versus high (quartile 4) serum selenium levels on survival from laryngeal cancer.
Jim's Conclusions: Thus, the study concludes that serum selenium levels >70 μg/l are associated with improved survival in patients undergoing treatment for laryngeal cancer.