Prevention and Screening of Breast Cancer
Women who drink more than two alcoholic drinks per day are at increased risk for breast cancer, and exercise is associated with a decreased risk of breast cancer. Dietary intake has not been conclusively associated with breast cancer risk. Various models have been used to predict a woman's risk for breast cancer.
The National Cancer Institute has developed the Breast Cancer Risk Assessment Tool, which is based on the Gail Model, and calculates the woman's risk of developing breast cancer in the next 5 years by considering the following factors:
- The woman's age,
- Age at which she had her first menstrual period,
- Age at delivery of first live child,
- Number of first-degree relatives with breast cancer,
- History of any breast biopsies, and
- History of atypical hyperplasia.
The model has been validated in white women and has been evaluated in black women and found to be relatively accurate, although it may underestimate the risk in black women with a history of previous breast biopsies. It has yet to be validated in women of other ethnicities.
In addition to lifestyle modifications, such as exercise and moderation of alcohol intake, chemoprevention of breast cancer is an option for some women. The selective estrogen receptor modifiers (SERMS) tamoxifen and raloxifene have both been shown to reduce invasive breast cancer in high-risk women.
However, there are risks associated with SERM treatment. Tamoxifen is associated with an increased risk of endometrial cancer and deep venous thrombosis (DVT). Although raloxifene is not associated with an increased risk of endometrial cancer, the risk of DVT remains.
The clinicians discuss chemoprevention with women at high risk for breast cancer and at low risk for the adverse effects of chemoprevention. Clinicians should inform patients of the potential benefits and harms of chemoprevention. Breast cancer risk increases with age, but the risk of adverse effects does as well. Since the clinical trials of tamoxifen and raloxifene for breast cancer prevention used a 1.66% 5-year risk, this risk level is often used as a guide for treatment.
Traditional breast cancer screening modalities include screening mammography, clinical breast examination, and breast self-examination. Teaching women to do routine breast self-examination has not been shown to reduce breast cancer mortality.
The American Cancer Society states that it is acceptable not to do it, but that if women are performing breast self-examination, it is important to ensure that they are doing it correctly. The combination of breast examination done by a clinician and mammography is associated with a decrease in breast cancer mortality, but there is insufficient evidence to recommend clinical breast examination alone.
Mammography reduces breast cancer mortality in women aged 50-74 years and routine mammographic screening is recommended for women in this age group. For women aged 40-49 years, screening has been more controversial. It has been recommended that clinicians not routinely order mammography among 40- to 49-year-old women but rather that they individualize the decision to begin screening, since the number needed to invite to screen to prevent one breast cancer death is much higher in younger women and the number of false-positive and false-negative test results are much higher.
Since women over age 75 have not been included in clinical trials and since the likelihood of comorbid diseases limiting life expectancy increases, routine screening of women in this age group is not recommended, but rather the decision making should be individualized.