There are a number of factors that can increase your risk of developing breast cancer. The most important and least discussed is increasing age. Less than 5% of breast cancers occur before age 40. Between ages 40 through 49, a woman has a 1.5% (1 in 66) risk of developing breast cancer. In successive decades, the risk is higher. Between ages 50 through 59 years, your risk increases to 2.5% (1 in 40); between ages 60 through 69 years, your risk increases to 3.4% (1 in 29). As measured by the number of new cases per 100,000 women, age-specific incidence increases from 163 cases per 100,000 women in the group aged 40 through 49 up to 480 per 100,000 women in the group aged 75 through 79. After age 80, it decreases slightly to 431 per 100,000 women 85 years of age and older.

"Hormonal" risk factors include early age of menarche (first menses), late menopause, first childbirth after age 30, and nulliparity (never having been pregnant). Long-term estrogen use is associated with an increased risk of developing breast cancer. Atypical ductal hyperplasia identified by breast biopsy increased one's risk, as does lobular carcinoma in situ, moderate-to-florid ductal hyperplasia, and papillomatosis.

A History of exposure of the chest to radiation can increase risk. Data from the Late Effects Study Group show that women receiving thoracic radiation in the second and third decades of life have a 35% risk of developing breast cancer by age 40. This is radiation used for theraputic purposes, not mammography.

A family history of breast cancer can significantly increase risk. A first-degree relative (sister, mother, father) with breast cancer is much more significant than other, more distant affected relatives would be. The younger the first-degree relative was at the time they developed breast cancer, the greater your risk. Documented inheritance of the BRCA1 and BRCA2 gene increases one's lifetime risk for breast cancer by 56% to 85%.

Lifestyle factors associated with increased risk include alcohol use and obesity in the postmenopausal years.

The assessment of one's risk of developing breast cancer a detailed personal and family history. In the past, this historical information has given the physician an "impression" of risk but not an numerical risk assessment. We now have computer programs for risk assessment.

The National Cancer Institute has produced a computer program for risk assessment based on the Gail model of breast cancer risk. With this tool, a physician can define a patient's 5-year and lifetime risk for developing breast cancer as compared to women of the same age without those risk factors. This model has some limitations. For instance, it does not account for early age of diagnosis in affected relatives.

At The University of Texas Southwestern Medical Center at Dallas, a risk assessment program called CancerGene has been developed by David Euhus, MD. This computerized assessment uses several mathematical models to calculate risk and better incorporates issues of familial risk. The program can assess the magnitude of risk for genetic mutations, allowing physicians to select those women who would benefit most from genetic testing.

A formal risk assessment allows a physician to tailor recommendations for surveillance and prevention on the basis of the individual patient's profile. NCCN has made recommendations for women at increased risk. For women under 25 years of age who have had prior thoracic radiation or have a proven genetic predisposition, they recommend annual physical and breast examination. After age 25, recommendations call for annual mammography with physical examination every 6 months and monthly BSE. For women over 25 years of age with radiation exposure, mammography screening typically begins 10 years after radiation.

To define those women with genetic predisposition, NCCN uses the criteria proposed by the American Society of Clinical Oncology. Among women with genetic predisposition, annual mammography should begin 5 to 10 years before the earliest age of onset in the family but not before age 25 years.

One must remember that breast cancer screening is not preventive. Screening can result in the detection of in situ breast cancer (DCIS), which can be treated and cured, This prevents the development of an invasive breast cancer. Cancer "screening" is meant to make the diagnosis as early as possible.

Preventing the development of breast cancer is another unrelated problem. Physicians have several options for preventing the development of breast cancer. None are ideal. These include prophylactic mastectomy, tamoxifen therapy for 5 years, clinical trial participation, and diet and lifestyle modification

While extreme, mastectomy is highly effective in preventing breast cancer, with efficacy in studies cited as high as 90% to 97%. Studies of women who have undergone prophylactic mastectomy have shown that more than 90% of women have no regret over their decision for surgery.

Results from the Breast Cancer Prevention Trial of the National Surgical Adjuvant Breast and Bowel Project (NSABP) have shown that tamoxifen can reduce breast cancer risk by 50%. This resulted in Food and Drug Administration approval of tamoxifen as a preventative agent for women at increased risk. However, many questions remain about chemoprevention. Clinical trials offer an avenue to address these questions and help find the ideal prevention agent. This search for the ideal preventative agent has led to the second NSABP prevention trial: the STAR (Study of Tamoxifen and Raloxifene) trial which opened in 1999. This trial randomizes postmenopausal women at increased risk for breast cancer between tamoxifen and raloxifene. Postmenopausal women older than 60 years and postmenopausal women with lobular carcinoma in situ qualify automatically for entry, and postmenopausal women aged 35 through 59 years qualify if their calculated risk is high.

For many women, taking a drug to prevent breast cancer is not the most ideal option. They prefer to identify lifestyle, dietary, and environmental factors that they can modify to prevent the disease. Recent studies show no evidence that lowering the amount of fat in the diet will decrease risk. Some data, however, suggests that women should avoid obesity (particularly in their postmenopausal years), reduce alcohol intake, and adopt a program of moderate exercise to reduce their risk of breast cancer.

If the physician or patient believes there is an increased risk for breast cancer, this must be confirmed objectively with a formal risk assessment. This allows the physician and patient to weigh the risk of breast cancer against the risks of other medical problems, such as heart disease and osteoporosis. After this is done, prevention strategies can be considered, with their respective benefits and risks. Women who prefer chemoprevention should consider participation in a clinical trial. Since only postmenopausal women are eligible for the STAR trial, premenopausal women will be candidates for tamoxifen, which is the only agent approved for prevention of breast cancer. For these women, quality-of-life issues relative to estrogen deficiency must be weighed. These decisions should be made with careful consideration of all issues. The decision-making process will take time. After careful deliberation, many women may choose close observation with clinical examination and mammography in the attempt to detect breast cancer as early as possible.