In our study we have investigated whether selenium concentration can be used as valuable marker for early detection of cancers in a group of individuals with CHEK2 mutations and in unselected patients. We found very significant association of higher selenium concentration with lower probability of cancer detection in tested groups. This observation is particularly valuable for individuals carrying CHEK2 mutation, who have increased risk of cancer. We also found some evidences for association of rs1139793 in TXNDR2 and rs5845 in SEP15 with cancer risk in CHEK2 carriers, what might be useful...