Postdiagnosis Cruciferous Vegetable Consumption and Breast Cancer Outcomes: A Report from the After Breast Cancer Pooling Project

Abstract

Cruciferous vegetables are a major source of glucosinolate-derived bioactive compounds such as isothiocyanates, which have been shown in animal and in vitro studies to inhibit cancer growth and progression. Few studies have investigated cruciferous vegetable intake after diagnosis and breast cancer outcomes. Using data from the After Breast Cancer Pooling Project, which includes prospective data from US and Chinese breast cancer survivors, we evaluated the association of cruciferous vegetables with breast cancer outcomes. Analyses included 11,390 women diagnosed with stage I–III invasive breast cancer (1990–2006) from four cohorts. Cruciferous vegetable intake (g/day) was assessed using food frequency questionnaires (mean of 22 months post-diagnosis). Study heterogeneity was evaluated by the Q statistic; hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using delayed-entry Cox regression models stratified by study. After a median follow-up of 9.0 years, 1,725 deaths and 1,421 recurrences were documented. In pooled analyses using study-specific quartiles, cruciferous vegetable intake was not associated with breast cancer outcomes, adjusting for known clinical prognostic factors and selected lifestyle factors. HRs (95%CIs) by increasing quartiles (reference=lowest quartile) were 1.08 (0.93–1.25), 1.01 (0.87–1.18), and 1.10 (0.95–1.28) for recurrence (Ptrend=0.34) and 1.01 (0.88–1.15), 0.97 (0.84–1.11), and 0.99 (0.86–1.13) for total mortality (Ptrend=0.84). No associations were observed for subgroups defined by ER status, stage, or tamoxifen therapy. Cruciferous vegetable intake at approximately two years after diagnosis was not associated with recurrence or mortality. Our results do not support an association between post-diagnosis cruciferous vegetable intake and breast cancer outcomes.

Chemopreventive properties of 3,3′-diindolylmethane in breast cancer: evidence from experimental and human studies

“…The protective effect reached a significant 35% decrease in women on adjuvant tamoxifen therapy. A pooling of 4 cohorts of women with stages I-III breast cancer by Nechuta et al 11 showed no significant associations between intake of cruciferous vegetables and breast cancer recurrence or total mortality after a median follow-up of 9 years. In addition to variations in intake across studies, particularly within the highest quartiles, measurement errors in dietary assessment limit the interpretation of the epidemiological evidence.…”

“…Overall, point estimates of the odds ratio and relative risk suggest a protective role, though less so in US studies. 1,3,4,9 This may be due to the overall lower intakes in the United States, 11 particularly in comparison with intakes in Asian countries, where the risk of breast cancer is lower among those with greater intakes. 5,7,8 A recent meta-analysis of 13 case-control and prospective cohort studies and 18 673 individual cases suggested that overall high intake of cruciferous vegetables was significantly associated with a 15% lower risk of breast cancer.…”

“…Cruciferous vegetables have been shown to be protective against breast cancer in some, [1][2][3][4][5][6][7][8] but not all, [9][10][11] epidemiological studies. Discrepancies in current findings are thought to be explained in part by variances in exposure to multiple bioactive constituents found in this unique classification of vegetables.…”

Phenethyl isothiocyanate: A comprehensive review of anti-cancer mechanisms

“…Although none of these studies provide a direct correlation between cancer incidence and intake of a specific ITC, many studies do identify a correlation between the total ITC intake in the form of cruciferous vegetables and reduced risk of several types of cancers in lung, breast, gastric, bladder, colorectal, pancreatic, prostate and kidney (Table 1) [5, 8–27]. Interestingly, there are also few studies where the results obtained were opposite to the preventive effects of cruciferous vegetables.…”

Nutritional Epidemiology—There's Life in the Old Dog Yet!

“…One study of breast cancer showed improved survival associated with a greater variety in consumption of vegetables and fruit and of fruit alone (75) and one showed reduced recurrence with higher intake of vegetables (76). A third breast cancer study showed no association between survival or recurrence and intake of cruciferous vegetables (77). One study of prostate cancer showed reduced likelihood of progression associated with higher intake of cruciferous vegetables (78).…”