Can breast cancer be prevented?

Can breast cancer be prevented?
At this time, there is no guaranteed way to prevent breast
cancer, which is why regular mammograms are so
important. A woman’s best overall preventive health
strategy is to reduce her known risk factors as much as
possible by avoiding weight gain and obesity, engaging in
regular physical activity, and minimizing alcohol
intake.65 Women should consider the increased risk of
breast cancer associated with HRT use when evaluating
treatment options for menopausal symptoms. Treatment
with tamoxifen or raloxifene can also reduce the
risk of breast cancer among women at high risk (see page
12, section on chemoprevention).
Obesity
Obesity increases risk of postmenopausal (but not
premenopausal) breast cancer, as does weight gain
during adulthood.67-71 A recent study found that women
who gained 55 pounds or more after age 18 had almost
1.5 times the risk of breast cancer compared with those
who maintained their weight. A gain of 22 pounds or
more after menopause was associated with an increased
risk of 18%, whereas losing at least 22 pounds after
menopause and maintaining the weight loss was
associated with 57% lower breast cancer risk.71 In postmenopausal
women, circulating estrogen is primarily
produced in fat tissue. Thus, having more fat tissue
increases estrogen levels and the likelihood of develop-
Table 4. Age-Specific Probabilities of
Developing Invasive Breast Cancer*
The probability of
If current developing breast cancer
age is: in the next 10 years is: or 1 in:
20 0.05% 1,837
30 0.43% 234
40 1.43% 70
50 2.51% 40
60 3.51% 28
70 3.88% 26
Lifetime risk 12.28% 8
*Among those free of cancer at beginning of age interval. Based on
cases diagnosed 2002-2004. Percentages and “1 in” numbers may
not be numerically equivalent due to rounding.
Data source: DevCan Software, Version 6.2.1.165
American Cancer Society, Surveillance Research, 2007
ing breast cancer. Given the large percentage of women
in the US who are overweight or obese, strategies to
maintain a healthy body weight are important to reduce
the risk of both developing and dying from breast cancer.
Physical activity
Growing evidence supports a small protective effect of
physical activity on breast cancer.67,72-75 Although most
studies find reduced risk in women who exercise
vigorously for 45 to 60 minutes on 5 or more days per
week, one study suggests that regular physical activity,
regardless of intensity, may reduce the risk of breast
cancer in postmenopausal women.66,73 Overall, the
protective effect of physical activity may be greatest
among lean women, women who have carried children
to term, and premenopausal women. The underlying
mechanism of this potential protection is not well
understood, although it has been hypothesized that the
benefit may be due to the effects of physical activity on
hormones and energy balance.67,76
Alcohol consumption
Alcohol consumption is consistently associated with
increased breast cancer risk.77-80 A meta-analysis of more
than 40 epidemiologic studies suggests that the
equivalent of 2 drinks a day (or 24g of alcohol) may
increase breast cancer risk by 21%. This increased risk is
dose-dependent and exists regardless of the type of
12 Breast Cancer Facts & Figures 2007-2008
alcoholic beverage consumed. A recent review
concluded that the most likely mechanism by which
alcohol increases risk of breast cancer is by increasing
estrogen and androgen levels.81 Thus, reducing alcohol
intake may be a useful strategy for reducing breast
cancer risk among regular consumers of alcohol.