It's great to see a 7% drop in the number of women were diagnosed with breast cancer in 2003. There was an even bigger drop in hormone-receptor positive breast cancers (about 15%). Of course, we want to see this drop continue year after year (let's make the number of cases go down to zero!) and we also want to know what made this drop happen (what can women do to reduce their own risk of getting breast cancer?).
In an effort to explain the finding and give women a better "recipe" for good breast health, researchers looked for answers. They noticed a big decrease in the use of hormone replacement therapy (HRT) in 2002 after the release of the Women's Health Initiative Study. This study showed a higher risk of breast cancer in women taking estrogen/progestin HRT after menopause (as well as no protection against heart disease). This kind of hormone replacement therapy is associated with a higher risk of hormone-receptor positive breast cancer. When the researchers saw that the drop in breast cancer cases occurred soon after large numbers of women stopped taking HRT, they thought there might be a link between these two events.
While this link might be real, it's probably only one of several explanations. Breast cancer takes years to grow. The increased risk of breast cancer seen in women on HRT is usually observed after several years of use. So it makes sense that any drop in the number of cases of breast cancer would only come years after getting off HRT (not the short time seen in this study).
We need to study the use of HRT and the incidence of breast cancer over several years to better understand the possible connection—not just one or two years. Plus other factors need to be considered. For example, if significantly fewer women had mammograms during that same time period, then fewer breast cancers would be detected—we can't say for certain that it is solely due to the decline in HRT use.
We want to help all women avoid breast cancer entirely. Avoiding HRT is one important step in risk reduction. Other important steps include: get and stick to your ideal body weight, get 3-4 hours of exercise per week, eat a low fat diet with 5-9 fruits and vegetables a day, do NOT smoke, limit alcohol use to less than 5 drinks per week. Women at high risk for breast cancer (strong family history, having the breast cancer gene abnormality or a personal history of breast cancer) may consider risk-reducing medications and possible prophylactic surgery. Stay tuned to breastcancer.org for more updates on this very important subject.