Inverse associations between plasma lycopene and other carotenoids and prostate cancer

Although dietary intake of tomatoes and tomato products containing lycopene has been reported to reduce the risk of prostate cancer, few studies have been done on the relationship between plasma lycopene and other carotenoids and prostate cancer. This case-control study was conducted to investigate the effects of plasma lycopene, other carotenoids, and retinol, as well as alpha- and gamma -tocopherols on the risk of prostate cancer. The study inc luded 65 patients with prostate cancer and 132 cancer-free controls; all of them were interviewed using a standard epidemiological questionnaire at th e Memorial Sloan-Kettering Cancer Center from 1993 to 1997. Plasma levels o f carotenoids, retinol, and tocopherols were measured by high performance l iquid chromatography. An unconditional logistic regression model was used i n bivariate and multivariate analyses using Statistical Analysis System (SA S). After adjusting for age, race, years of education, daily caloric intake , pack-years of smoking, alcohol consumption, and family history of prostat e cancer, significantly inverse associations with prostate cancer were obse rved with plasma concentrations of the following carotenoids: lycopene [odd s ratio (OR), 0.17; 95% confidence interval (CI), 0.01-0.78; P for trend, 0 .0052] and zeaxanthin (OR, 0.22; 95% CI, 0.06-0.83; P for trend, 0.0028) wh en comparing highest with lowest quartiles. Borderline associations were fo und for lutein (OR, 0.30; 95% CI, 0.09-1.03; P for trend, 0.0064) and beta -cryptoxanthin (OR, 0.31; 95% CI, 0.08-1.24; P for trend, 0.0666). No obvio us associations were found for alpha- and beta -carotenes, retinol, and alp ha- and gamma -tocopherols. Our study confirmed the inverse associations be tween lycopene, other carotenoids such as zeaxanthin, lutein, and beta -cry ptoxanthin, and prostate cancer. This study provides justification for furt her research on the associations between lycopene and other antioxidants an d the risk of prostate cancer.