Background Epidemiological studies examining associations between carotenoid intakes and risk of breast cancer by estrogen receptor (ER) and...
Background Epidemiological studies examining associations between carotenoid intakes and risk of breast cancer by estrogen receptor (ER) and progesterone receptor (PR) status are limited.
Objective We investigated these associations in a pooled analysis of 18 cohort studies.
Design Among 1,028,438 participants followed for with maximum follow-up of 26 years across studies, 33,380 incident invasive breast cancers were identified. Study-specific relative risks (RRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression and then pooled using a random-effects model.
Results Alpha-carotene, beta-carotene and lutein/zeaxanthin intakes were inversely associated with risk of ER- breast cancer (pooled multivariable RRs comparing the highest with lowest quintile =0.87 (95%CI: 0.78-0.97) for alpha-carotene, 0.84 (95%CI: 0.77-0.93) for beta-carotene and 0.87 (95%CI: 0.79-0.95) for lutein/zeaxanthin) but not ER+ breast cancer (pooled multivariable RRs for the same comparison = 1.04 (95%CI:0.99-1.09) for alpha-carotene, 1.04 (95%CI: 0.98-1.10) for beta-carotene and 1.00 (95%CI: 0.93-1.07) for lutein/zeaxanthin. Although the pooled RRs for quintile 5 for beta-cryptoxanthin were non-significant, inverse trends were observed for ER- and ER+ breast cancer (Ptrend ? 0.05). Non-significant associations were observed for lycopene intake. The associations were largely not appreciably modified by several breast cancer risk factors. Non-significant associations were observed for PR+ and PR- breast cancer.
Conclusions Intakes of alpha-carotene, beta-carotene and lutein/zeaxanthin were inversely associated with risk of ER- , but not ER +, breast cancer. However, results need to be interpreted with caution because it is unclear whether the observed association is real or due to other constituents in the same food sources.