Serum beta-carotene in persons with cancer and their immediate families.

A unique case-control study design including family members of cases and controls was used to assess the association between serum beta-carotene and cancer. The cases (n = 389) were incident cancer cases diagnosed between 1981 and 1984 in Wellington, New Zealand, and the controls (n = 391) were hospital patients without cancer. Both cases and controls were on a home diet at the time beta-carotene levels were measured. Since findings concerning patients who have already been diagnosed with cancer may reflect changes that occurred subsequent to development of cancer, family members of cancer patients (n = 618) and control patients (n = 675) were included, giving a total of 2,073 study participants. Low levels of beta-carotene were observed for individuals with a number of cancers, including cancers of the lung stomach, esophagus, small intestine, cervix, and uterus. Low levels of beta-carotene were also found in the relatives of these cancer patients. These differences persisted after stratification by current cigarette smoking. The strongest findings were those for lung cancer. Excluding adenocarcinoma, lung cancer patients had average serum beta-carotene levels of 40.2 micrograms/dl, 25.9 micrograms/dl lower than those of controls, adjusted for age, sex, and length of sample storage (p less than 0.01). Family members of the lung cancer patients also had lower values than family members of control patients, with an adjusted difference of 10.8 micrograms/dl (p less than 0.01). Odds ratio estimates for lung cancer by quartiles of beta-carotene residuals ranged from 3.6 (90% confidence interval (CI) 1.1-12.2) for the second-highest quartile to 6.6 (90% CI 1.9-23.0) for the lowest quartile (test for trend, p less than 0.001). Patients with cancers of the breast, colon, prostate, and skin did not have lower levels of serum beta-carotene than expected. Family members of individuals with these cancers also did not have lower levels of serum beta-carotene. The cancer sites that were associated with serum beta-carotene are, in general, sites for which smoking is a strong risk factor, and the sites that were not associated with beta-carotene do not have smoking as a risk factor.