Abstract 1266: Racial differences in the association of cruciferous vegetable intake with breast cancer hormone receptor status and tumor subtype
Authors: Tang Li , Kwan Marilyn L. , Yao Song , Roh Janise M. , Laurent Cecile A. , Hershman Dawn L. , Kumar Schicha , Wilding Gregory E. , Ambrosone Christine B. , Kushi Lawrence H. 
Published: May 2015

Background: Dietary isothiocyanates (ITCs) are chemopreventive phytochemicals from cruciferous vegetables (CV). ITCs down-regulate estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) in breast cancer cells, and inhibit development of breast cancer in animal models. CV intake was found to be inversely associated with breast cancer risk. However, the association of CV intake with breast cancer subtype is unknown. Further, racial differences exist in dietary habits and polymorphic genes in ITC-metabolizing pathway. In a prospective cohort, we examined the association of prior CV intake with breast cancer hormone receptor status and subtype by race.

Methods: Among 2908 breast cancer patients diagnosed 2005-2013 at Kaiser Permanente Northern California (KPNC), data on CV intake in the past 6 months were obtained from a validated food frequency questionnaire as part of a comprehensive baseline interview about two months post-diagnosis. Breast cancer characteristics came from the KPNC Cancer Registry. CV intake and its association with hormone receptor status (ER+/-, PR+/-, and HER2+/-) and subtype (luminal A/luminal B/triple negative/HER2-overexpressing) were examined among Whites, African Americans (AA), Asians, and Hispanics. Logistic regression was used adjusting for age at diagnosis, race, menopausal status, parity, energy intake, and dietary fiber from vegetables.

Results: CV intake (grams/day) differed across racial groups (p&lt;0.01), with 46.9, 35.6, 30.7, and 27.8 for Asians, AA, Whites, and Hispanics, respectively. Except for broccoli, intake of other individual CVs differed across racial groups (p&lt;0.01). Total CV intake was not associated with breast cancer subtypes in any racial group. However, compared with PR+ disease, coleslaw intake was associated with reduced odds of PR- disease in Asians (high vs. low: OR=0.63, 95%CI=0.41-0.97), while intake of greens including collard, kale, turnip and mustard was associated with increased odds of PR- disease in Whites (high vs. low: OR=1.34, 95%CI=1.09-1.66). Broccoli and cabbage intake were associated with reduced odds of HER2+ disease in Asians, compared with HER2- disease (high vs. low: OR=0.46, 95%CI=0.23-0.94 for broccoli, and OR=0.48, 95%CI=0.24-0.95 for cabbage). No associations were observed for Hispanics and AAs. In all racial groups combined, total CV intake, specifically broccoli intake, was associated with increased odds of luminal B, compared with luminal A subtype (OR=1.83, 95%CI= 1.19- 2.79). However, the association became null with increasing broccoli intake.

Discussion: The association of CV intake with breast cancer characteristics varied by race and by individual CV. The differences may be attributable to diverse genetic background among racial groups, and specific ITCs in individual CVs.

Funded by K07 CA148888 and R01 CA105274

Citation Format: Li Tang, Marilyn L. Kwan, Song Yao, Janise M. Roh, Cecile A. Laurent, Dawn L. Hershman, Schicha Kumar, Gregory E. Wilding, Christine B. Ambrosone, Lawrence H. Kushi. Racial differences in the association of cruciferous vegetable intake with breast cancer hormone receptor status and tumor subtype. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1266. doi:10.1158/1538-7445.AM2014-1266