Serum micronutrients and risk of cancers of low incidence in Finland.

The associations between serum alpha-tocopherol, beta-carotene, retinol, retinol-binding protein, and selenium levels and the subsequent occurrence of different cancers of low incidence were investigated in a nested case-control study of 39,268 men and women participating in the Social Insurance Institution's Mobile Clinic Health Examination Survey in Finland. During follow-up from the baseline in 1968-1972 to the end of 1977, a total of 115 cancers of the lip, oral cavity, pharynx, larynx, esophagus, liver, gallbladder, kidney, urinary bladder, brain, and skin were reported to the nationwide Finnish Cancer Registry. Alpha-tocopherol, beta-carotene, retinol, retinol-binding protein, and selenium concentrations were determined from stored serum samples collected from these cancer cases and matched controls at baseline. Several sites indicated an elevated risk of cancer at low levels of the serum variables, although only a few of these associations were statistically significant. Only melanoma patients had significantly lower serum alpha-tocopherol and beta-carotene levels than corresponding controls. Since the numbers of cancer cases were small, no firm conclusions can be drawn from these results until they have been confirmed in studies based on larger cohorts or on pooled data from several small samples.