Selenium levels during the course of radiotherapy. No influence of irradiation on blood selenium concentration

To evaluate the influence of tumor characteristics and irradiation on blood selenium concentrations and their course during radiotherapy.

Selenium Levels were determined at various times during radiotherapy (I: beginning, II: mid, III: end, IV: 6 weeks after) by atomic absorption spectrometry in whole blood. The values were correlated with patient-, tumor- and irradiation-related parameters.

A total of 690 samples were analyzed in 224 patients. The mean selenium value was 75.64 microg/l at the beginning of radiotherapy. 170 patients (77%) had reduced selenium Levels < 89 microg/l. Twelve patients (5.4%), mostly with head-and-neck cancer, had critically low values which need to be controlled and monitored. Three patients (1.3%) with breast cancer had critically increased values. Female patients showed higher seLenium concentrations than male patients (p = 0.0404). Patients diagnosed for head-and-neck cancer had significantly lower seLenium values than breast cancer patients (p = 0.016). Previous treatment by surgery and/or chemotherapy was correlated with lower selenium concentrations compared with irradiation as primary treatment (p = 0.039). According to analysis of variance, there was no significant change of the selenium concentration during the course of radiotherapy (p > 0.05).

A preexisting selenium deficiency could be diagnosed in the broad majority of cancer patients undergoing radiotherapy. In contrast to the widely held opinion, it was not further aggravated by standard radiotherapy protocols.