Fruit and vegetable intake and risk of breast cancer by hormone receptor status

Background Estrogen receptor-negative (ER^-) breast cancer has few known or modifiable risk factors. Because ER^- tumors account for only 15% to 20% of breast cancers, large pooled analyses are necessary to evaluate precisely the suspected inverse association between fruit and vegetable intake and risk of ER^- breast cancer. Methods Among 993 466 women followed for 11 to 20 years in 20 cohort studies, we documented 19 869 estrogen receptor positive (ER⁺) and 4821 ER^- breast cancers. We calculated study-specific multivariable relative risks (RRs) and 95% confidence intervals (CIs) using Cox proportional hazards regression analyses and then combined them using a random-effects model. All statistical tests were two-sided. Results Total fruit and vegetable intake was statistically significantly inversely associated with risk of ER^- breast cancer but not with risk of breast cancer overall or of ER⁺ tumors. The inverse association for ER^- tumors was observed primarily for vegetable consumption. The pooled relative risks comparing the highest vs lowest quintile of total vegetable consumption were 0.82 (95% CI = 0.74 to 0.90) for ER ^- breast cancer and 1.04 (95% CI = 0.97 to 1.11) for ER⁺ breast cancer (P_{common-effects} by ER status <. 001). Total fruit consumption was non-statistically significantly associated with risk of ER ^- breast cancer (pooled multivariable RR comparing the highest vs lowest quintile = 0.94, 95% CI = 0.85 to 1.04). Conclusions We observed no association between total fruit and vegetable intake and risk of overall breast cancer. However, vegetable consumption was inversely associated with risk of ER^- breast cancer in our large pooled analyses.