Abstract A90: Plasma carotenoids and risk of breast cancer: Pooled analysis of eight prospective cohorts
Authors: Eliassen A. Heather , Hendrickson Sara J. , Dorgan Joanne F. , Hallmans Goran , Helzlsouer Kathy J. , Sesso Howard D. , Zeleniuch-Jacquotte Anne , Toniolo Paolo , Dai Qi , Goodman Marc T. , Campos Hannia , Hankinson Susan E. 
Published: January 2011

Abstract
Carotenoids, prominent micronutrients in fruits and vegetables that act as antioxidants, may reduce the risk of breast cancer. Several studies of plasma carotenoids and breast cancer have been conducted and most, but not all, have found an inverse association with at least one carotenoid although the specific carotenoid has varied across studies. We conducted a pooled analysis of eight cohort studies comprising &gt;95% of the world's published prospective data on plasma carotenoids and breast cancer. The studies included 3,055 cases and 3,955 matched controls from the Columbia Missouri Breast Cancer Serum Bank; MSP/VIP/MONICA cohorts in Umea, Sweden; Johns Hopkins University CLUE I and II; Nurses’ Health Study; Women's Health Study; New York University Women's Health Study; Shanghai Women's Health Study; and Multiethnic Cohort Study. To account for laboratory differences and examine population differences across studies, we recalibrated participant carotenoid levels by re-assaying 20 plasma samples from each cohort together at the same laboratory. Recalibration data are currently available for seven of the eight cohorts; recalibration data from the 8th cohort are being incorporated. Using conditional logistic regression, adjusted for several breast cancer risk factors, we first calculated relative risks (RRs) and 95% confidence intervals (CIs) from each study, using study-specific quintiles, and pooled the estimates using a random effects model weighted by the inverse variances. Next we recalibrated carotenoid levels from each study to a common standard and conducted conditional logistic regression on the pooled data using quintiles defined among the controls from all studies. Levels of carotenoids differed across cohorts (e.g., median recalibrated lycopene ranged from 17.9 (Umea) to 41.9 (NHS) μg/dL) as did the primary contributor to total carotenoids (ß-carotene, lutein/zeaxanthin, or lycopene). Total carotenoids were suggestively inversely associated with breast cancer risk when study-specific RRs were pooled (top vs. bottom study-specific quintile RR=0.72,95% CI (0.51 −1.01), p-trend=0.07), but with significant heterogeneity across studies (p=0.002). Using recalibrated carotenoid levels and common quintiles, significant inverse associations with breast cancer were observed for α-carotene (top vs. bottom common quintile RR=0.82,95% CI (0.68-0.99), p-trend=0.01), ß-carotene (comparable RR=0.75,95% CI (0.62-0.90), p-trend=0.002), lutein/zeaxanthin (comparable RR=0.80,95% CI (0.67-0.97), p-trend=0.03), and total carotenoids (comparable RR=0.79,95% CI (0.65-0.97), p-trend=0.01). ß-cryptoxanthin (comparable RR=0.93,95% CI (0.76-1.13), p-trend=0.07) and lycopene (comparable RR=0.91,95% CI (0.74-1.12), p-trend=0.18) were not significantly associated with breast cancer risk. Tests for heterogeneity using recalibrated data were not significant. This comprehensive prospective analysis suggests women with higher plasma levels of a-carotene, ß-carotene, lutein/zeaxanthin, and total carotenoids may be at reduced risk of breast cancer.
Citation Information: Cancer Prev Res 2010;3(12 Suppl):A90.