Vitamin D and selenium blood levels and acute skin toxicity during radiotherapy for breast cancer

•Among breast cancer patients undergoing radiotherapy Vitamin D deficiency is common.•We found no correlation between skin toxicity, vitamin D and selenium blood levels.•Skin toxicities correlated significantly with breast size and skin thickness. Vitamin D blood levels have been shown to influence acute chemotherapy toxicities. Therefore, it was investigated whether it is an intrinsic factor influencing acute skin toxicity in patients receiving radiotherapy for breast cancer. In a total of 107 patients receiving radiotherapy for resected breast cancer, vitamin D and selenium blood levels were determined. Correlations between these levels and skin toxicity due to radiotherapy (CTC scores, Skindex scores) were investigated as primary endpoints. Furthermore, the statistical relationship between skin toxicity, vitamin D and selenium blood levels with patient and disease characteristics such as tumor stage, breast size, skin thickness, blood cell counts as well as individual quality of life measured by SEIQoL-Q was analyzed. In our patient collective large deficiencies of vitamin D (mean level 20.9 ng/ml, normal range 36–60 ng/ml) and selenium (mean level 76.1 μg/l, normal range 74–139 μg/l) were found. No correlations between skin toxicities, vitamin D and selenium blood levels were found. Neither did these blood levels correlate with any tumor or patient characteristics nor with individual quality of life. As expected by clinical experience, skin toxicities correlated significantly with breast size and skin thickness. In this study, radiotherapy skin toxicity was not influenced by vitamin D or selenium blood levels. On the basis of our data we cannot recommend vitamin D or selenium supplementation as a prophylaxis for skin toxicity. Nevertheless, large numbers of breast cancer patients have substantial deficiencies of both substances. Therefore, supplementation may be reasonable for other reasons.