Plasma carotenoids and prostate cancer: A population-based case-control study in Arkansas.

A164

Prostate cancer is the most common cancer and second leading cause of cancer death in the US. Ecological and migrant studies strongly suggest that diet plays a crucial role in the etiology of this malignancy. Carotenoids are natural pigments synthesized by plants and microorganisms. These compounds possess antioxidant properties and have thus been hypothesized to protect against cancer. Epidemiological studies evaluating dietary carotenoids and prostate cancer have produced inconsistent results. Plasma carotenoids are biomarkers of dietary carotenoids, independent of recall bias inherent in dietary assessment. To date, however, few studies have investigated the relation between plasma carotenoids and prostate cancer. We examined the effects of plasma lutein/zeaxanthin, β-cryptoxanthin, trans-lycopene, cis-lycopene, total lycopene, α-carotene, trans-β-carotene, cis-β-carotene, and total β-carotene on prostate cancer risk, using data from 197 cases and 198 controls randomly selected from a large, population-based case-control study of prostate cancer in Arkansas. Plasma concentrations of cis-lycopene, trans-lycopene, and total lycopene were significantly lower in cases than in controls (all p<0.044). After adjustment for age, body mass index, education, and smoking, whites in the highest quartile of each of the measured plasma carotenoids exhibited a reduced risk of prostate cancer relative to those in the lowest quartile, although none of risk estimates attained statistical significance. Among blacks, a significant, remarkable reduction in risk was observed for cis-lycopene [OR(95% CI): 0.25(0.09-0.72)] and total lycopene [0.36(0.13-0.97)], whereas a significant, elevated risk was found for cis-β-carotene [(3.16(1.03-9.70)] and total β-carotene [(3.15(1.03-9.63)]. A protective effect of cis-lycopene, trans-lycopene, and total lycopene was detected for both young and middle-aged subjects (<65 years) and old subjects (≥65 years), but a dose-response reduction in risk was observed for the latter only (p-trend: 0.011 for cis-lycopene, 0.013 for trans-lycopene, and 0.008 for total lycopene). In summary, this study showed that plasma lycopene was inversely associated with prostate cancer risk, which was more pronounced among blacks and old individuals. A significant, increased risk with plasma β-carotene among blacks and an insignificant, reduced risk with the other carotenoids examined merit further investigation.