April 10, 2012 (Chicago, Illinois) — The consumption of cruciferous vegetables might have a positive impact on survival in breast cancer patients, according to the results of a new study.
The Shanghai Breast Cancer Survival Study, a large population-based prospective cohort study of Chinese breast cancer survivors, showed that eating cruciferous vegetables after a diagnosis of breast cancer was associated with improved survival in a population of Chinese women. The results were presented here at the American Association for Cancer Research 103rd Annual Meeting.
The researchers, led by Sarah J. Nechuta, MPH, PhD, a postdoctoral research fellow at Vanderbilt University in Nashville, Tennessee, found that after adjustment for confounders such as demographics, clinical characteristics, and lifestyle factors, cruciferous vegetable intake during the first 36 months after diagnosis was associated with a reduced risk for total mortality, breast-cancer-specific mortality, and recurrence.
They observed that across increasing quartiles of cruciferous vegetable consumption, the risk for total mortality decreased by 27% (to 62%), the risk for breast-cancer-specific mortality decreased by 22% (to 62%), and the risk for recurrence decreased by 21% (to 35%).
Population Differences
However, Dr. Nechuta cautioned that differences in the populations need to be taken into account when trying to extrapolate these results to other settings. "First, commonly consumed cruciferous vegetables in China include turnip, Chinese cabbage/bok choy, and greens, whereas broccoli and brussels sprouts are the most commonly consumed cruciferous vegetables in the United States and other Western countries," she told Medscape Medical News.
"Second, the amount of intake among Chinese women is much higher than that of American women," she continued. "The level of bioactive compounds, such as isothiocyanates and indoles, suspected of playing a role in the anticancer effects of cruciferous vegetables, depend on the amount and type of cruciferous vegetables consumed."
Future studies with direct measurements of bioactive compounds are needed to better understand the association between cruciferous vegetable intake and breast cancer outcomes, Dr. Nechuta noted.
She suggested that breast cancer survivors in the United States follow the general nutrition guidelines of eating vegetables daily, and consider increasing their intake of cruciferous vegetables, such as cabbage, cauliflower, and broccoli, as part of a healthy diet.
Chemopreventive Properties
The protective effect of cruciferous vegetables has been observed in other settings. Previous studies have reported that the intake of raw cruciferous vegetables, including broccoli, broccoli sprouts, cabbage, and cauliflower, was associated with a reduced risk for bladder cancer (Cancer Epidemiol Biomarkers Prev. 2008;17:938-944). The consumption of cruciferous vegetables might also help protect smokers from lung cancer, according to some data.
Preliminary research has shown that the consumption of broccoli sprouts can interfere with the development of gastritis and gastric cancer. In addition, consuming broccoli sprouts appears to enhance antioxidant and anti-inflammatory enzymes in the stomach, as previously reported by Medscape Medical News.
"In our 2002 study, sulforaphane killed helicobacter directly in the test tube," said Jed W. Fahey, MS, ScD, a nutritional biochemist in the Lewis B. and Dorothy Cullman Cancer Chemoprotection Center at the Johns Hopkins University School of Medicine, Baltimore, Maryland, in an interview at that time, referring to a previous study (Cancer Prev Res [Phila]. 2009;2:353-360). "It also reduced the rate of gastric cancer in mice."
"The key take-home message harkens back to the old message — eat veggies," Dr. Fahey told Medscape Medical News. "We're now giving people the science that shows why eating fruits and vegetables are good for your health."
Study Details
To evaluate the association between cruciferous vegetable consumption after cancer diagnosis and breast cancer outcomes, Dr. Nechuta and colleagues examined data on 4886 women with incident stage I to IV breast cancer, between the 20 and 75 years of age, who were recruited within 6 months of diagnosis from 2002 to 2006. Interviews were conducted to obtain data on clinical, sociodemographic, and lifestyle factors, and clinical data were verified with medical records.
The consumption of cruciferous vegetable was reassessed 18 and 36 months after diagnosis.
At a median follow-up of 5.3 years, there were 707 deaths and 666 recurrences in the study cohort. The intake of cruciferous vegetables increased after the diagnosis of cancer. Intake was associated with improved survival in a dose–response pattern (P for trend < .01)
The adjusted hazard ratios for the highest, compared with the lowest, quintiles were 0.42 for total mortality (95% confidence interval [CI], 0.33 to 0.54), 0.58 for breast-cancer-specific mortality (95% CI, 0.44 to 0.77), and 0.45 for nonbreast cancer mortality (95% CI, 0.26 to 0.78).
These associations remained after excluding the first year of follow-up, the researchers note. When looking at cancer recurrence, an inverse association was suggested, but it disappeared after the exclusion of the first year of follow-up.
Subgroup analyses, such as whether cruciferous vegetable intake benefited one group more than another, will be available at a later date, Dr. Nechuta explained.
American Association for Cancer Research (AACR) 103rd Annual Meeting: Abstract LB-322. Presented April 3, 2012.
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