Fruit and vegetable intake and postmenopausal breast cancer risk defined by estrogen and progesterone status

4165

Background: Fruit and vegetable intake has been inconsistently associated with a decreased risk of breast cancer. Some prospective studies have shown a protective association between certain classes of vegetables and breast cancer risk. Since it has been suggested that estrogen receptor (ER) and progesterone receptor (PR) status may identify a subgroup of breast cancers with different etiologies, the relationship between fruits and vegetables and breast cancer may vary by hormone receptor status. Methods: This study was conducted in The Swedish Mammography Cohort, a prospective cohort study of women in central Sweden, using data from 33,376 postmenopausal women who completed the 1997 questionnaire. Dietary intake of fruits and vegetables was assessed using a validated food frequency questionnaire (FFQ). Multivariate relative risks (RR) and 95% confidence intervals (CI) were calculated using Cox proportional hazards models. Women were followed from date of baseline questionnaire until date of breast cancer diagnosis, date of death, or end of follow-up, whichever came first. Results: A total of 817 postmenopausal breast cancers were identified between September 1997 and June2006. Hormone receptor status was available for 92% of the women with breast cancer (667 ER+ cases, 93 ER- cases, 460 PR+ cases, and 291 PR- cases). Total vegetable intake was not associated with an increased risk of ER+ postmenopausal breast cancer (RR=1.02, 95% CI 0.75 - 1.37 for 2.5 or more servings of vegetables per day versus less than 1 serving of vegetables per day) or ER- breast cancer (RR = 0.74, 95% CI 0.41 - 1.31 for 2.5 or more servings of vegetables per day versus less than 1 serving of vegetables per day). Total vegetable intake was not associated with the risk of PR+ or PR- breast cancer. Total fruit, citrus fruit, fruit juices, cruciferous vegetables, and leafy vegetables were not associated with ER+, ER-, PR+ or PR- breast cancer. When examining ER and PR status in combination, no association was observed between breast cancer and increased vegetable intake for ER+/PR+ (RR= 1.13, 95% CI 0.79 - 1.61 for 2.5 or more servings of vegetables per day versus less than 1 serving of vegetables per day), ER+/PR- (RR= 1.01, 95% CI 0.62 - 1.66 for 2.5 or more servings of vegetables per day versus less than 1 serving of vegetables per day), or ER-/PR- (RR=0.81, 95% CI 0.44 - 1.49 for 2.5 or more servings of vegetables per day versus less than 1 serving of vegetables per day). Additionally, no clear association was observed for any of the categories of fruits and vegetables and ER+/PR+, ER+/PR- or ER-/PR- breast cancer. Conclusion: Fruit and vegetable intake was not associated with an increased risk of hormone defined postmenopausal breast cancer in this large prospective study.