NcXHF

CAN DIET AND LIFESTYLE PREVENT BREAST CANCER?
TABLE 4. Current Evidence for Lifestyle and Breast Cancer Risk
Overall Effect Premenopausal Postmenopausal ER-positive ER-negative Family History BRCA1 BRCA2
Weight and adiposity Mixed effects * Mixed effects * Mixed effects
Lack of exercise Reduced effect * Mixed effects * Mixed effects
cf non family
history
Alcohol intake * No links found * No links found
Smoking during
adolescence/early
adulthood/lifelong
smoking
Lack of data No data No data No data
*Low-quality case-control data.
Association in three or more observational studies.
Association in one or two observational studies.
reduced with physical activity (especially if undertaken during
adolescence and early adulthood), with consistent null
effects of alcohol. 55,56 The limitations of these studies are well
recognized and large-scale prospective studies are required.
Recent prospective data from a New York cohort showed that
adherence to cancer prevention guidelines for a healthy
weight, reduced alcohol, and high physical activity reduced
breast cancer mortality by 61% (hazard ratio 0.39; 95% CI,
0.16 to 0.97) among BRCA1 and BRCA2 carriers. 57
THE ROLE OF LIFESTYLE AND RISK REDUCTION IN
THE GENOMIC ERA
Genome-wide association studies have identifıed more than
90 single nucleotide polymorphisms that are linked to breast
cancer risk. 58 Gene–environment interactions are an area of
increasing research interest with the potential to identify
women for whom particular risk factors and/or lifestyle
changes may be benefıcial. There are few data on gene–environment
interactions. An interaction between the CASP8-
rs1045485 polymorphism, which modifıes breast cancer
risk, and alcohol consumption has been replicated in a few
datasets. 59
LIFESTYLE PREVENTION OF BREAST CANCER
ACROSS THE LIFE COURSE
Although 75% to 80% of breast cancer cases in Western cohorts
occur after menopause, successful prevention of these
cases, and the 20% to 25% that are premenopausal, must start
earlier in life. Breast cancer risk can accumulate during childhood,
adolescence, and particularly in the period between the
menarche and fırst pregnancy before the breast cells become
differentiated and less susceptible to carcinogenesis (Table
2). Rates of growth in childhood and excess alcohol and
smoking in early adulthood increase risk, whereas soy intake
during these years may reduce risk. Weight gain during preand
postmenopausal years increases the risk of postmenopausal
(but not premenopausal) breast cancer. 60,61 Breast
cancer prevention interventions should therefore focus on
preventing weight gain during the premenopausal years.
Greater adiposity in childhood or early adulthood does
not increase breast cancer risk, and can sometimes put
women at lower risk. The reason for this weight paradox in
breast cancer is not clear but most likely reflects the fact
that heavier young women do not experience as much
weight gain during adulthood, and it is adult weight gain
that appears to put women at particularly high risk. Also,
young overweight women have lower serum progesterone
concentrations. 62
HOW CAN WE ENGAGE WOMEN IN BREAST CANCER
PREVENTION?
Recent expert reports estimate that successful lifestyle
changes could prevent 25% to 30% of cases of breast cancer. 63
However, there is a general public skepticism about whether
an individual’s actions can influence whether they develop
cancer. The most commonly cited perceived causes of breast
cancer are mainly out of the individual’s control, for example
genetics, environmental pollutants, pesticides, and God’s will
(Table 3). Although many women who develop breast cancer
have a genetic disposition, this is not the sole reason
why they develop breast cancer; in most cases a complex
interaction between genetic, reproductive, and lifestyle
factors is involved. 54
There is a need for consistent evidence-based cancer prevention
messages that are supported by good mechanistic
data to allow the public to understand and visualize the risk
information they receive. 64 Current evidence-based messages
are summarized in Table 4. These messages need to be
backed up with effective programs to support adherence at
key time points across the life course. There is increasing interest
in whether women attending breast screening can be
engaged in a healthy lifestyle to prevent breast cancer. 65 The
overlap between lifestyle recommendations for preventing
breast cancer and CVD (Table 1), as well as diabetes and dementia,
may be exploited to develop prevention programs for
multiple diseases in women.
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