A case control study of selenium in cancer.

As selenium has been shown to be a risk modifier of cancer at several sites in a case-control approach, selenium nutriture was studied in oral and oesophageal cancer patients. The mean selenium level in oral cancer patients was 102.6 ng/ml and in oesophageal cancer 103.3 ng/ml, while in the matched controls it was 117.5 and 116.2 ng/ml respectively. Relative risk estimates were 3.16 (P < 0.02) and 16.0 (P < 0.01) in oral and oesophageal cancer patients respectively. The risk appears to increase with selenium levels lower than 115 ng/ml.