Applied Evidence

Breast cancer prevention and Tx: An evidence-based guide

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When to begin screening mammography may be the latest controversy, but it’s not the only uncertainty regarding breast health and cancer care. We’ve culled the latest evidence to help you do what’s best.




Offer screening magnetic resonance imaging (MRI) to patients with a known BRCA 1 or 2 mutation, a strong family history of breast cancer, or a lifetime risk of breast cancer >20% to 25%. B

For early-stage breast cancer, lumpectomy and sentinel node mapping with excision is the preferred method for staging. A

Monitor patients receiving tamoxifen for signs and symptoms of venous thromboembolism, cataracts, and uterine malignancy, and patients on aromatase inhibitors for the development of osteoporosis. A

Strength of recommendation (SOR)

A Good-quality patient-oriented evidence
Inconsistent or limited-quality patient-oriented evidence
Consensus, usual practice, opinion, disease-oriented evidence, case series

Late last year, the US Preventive Services Task Force (USPSTF) sparked a nationwide controversy when it announced that it was recommending against routine screening mammography for women younger than age 50.1 Indeed, that’s a recommendation that many other organizations, including the American Cancer Society (ACS),2 the American College of Obstetricians and Gynecologists (ACOG),3 and the National Comprehensive Cancer Network (NCCN),4 disagree with. But the age at which women should begin routine mammography isn’t the only controversial question. Experts disagree on the benefits of breast self-examination, the optimal frequency of clinical breast exams, and the use of digital mammography—among other issues. This evidence-based review can help you cut through the confusion.

CASE Carrie, a 39-year-old woman who has never been pregnant, comes in for an annual Pap smear and gynecologic exam. She has a negative past medical history, but a positive family history for breast cancer—both her mother and 1 of her sisters had the disease. How would you assess Carrie’s risk of breast cancer, and what preventive measures would you recommend?

Use this predictive model to pinpoint your patient’s risk

When making decisions regarding primary prevention of and screening for breast cancer, an accurate assessment of risk is critical. Many predictive models have been developed with that in mind. The most widely studied, the Gail model, incorporates a number of important risk factors (TABLE 1), including age; race; family history; reproductive factors such as age of menarche, menopause, and first childbirth; and previous history of breast biopsy and atypical findings, to calculate a woman’s 5-year risk.5

A risk calculator (the Breast Cancer Risk Assessment Tool) based on the Gail model is available on the National Cancer Institute’s Web site, at Generally, a score ≥1.66%,5 which indicates that a patient has at least a 1.66% chance of developing breast cancer over the next 5 years, is considered high risk.6,7

CASE Carrie’s 2 first-degree relatives affected by breast cancer and her nulliparous status place her at increased risk. Further questioning reveals a particularly strong family history, as both relatives were diagnosed before the age of 50 (her mom at 45 years of age and her sister, at 39). Carrie’s 5-year risk is 1.8%.

Risk factors for breast cancer5,29

  • Age (>50 years)
  • Sex
  • Ethnicity*
  • Family history (≥1 first-degree relative diagnosed with breast cancer, particularly if diagnosed at <50 years of age)
  • Early menarche (<12 years)
  • Late menopause (>55 years)
  • Late age at first full-term pregnancy (>30 years)
  • Nulliparity
  • Breast density
  • History of breast biopsies
  • Atypical hyperplasia or LCIS on prior biopsy
  • History of radiation to chest wall
  • Lack of breastfeeding
  • Physical inactivity
  • Obesity
  • Alcohol use
  • Exogenous hormones (HRT)
*African American and Caucasian women are at higher risk compared with Asian, Hispanic, and Native American women.
1 drink/day results in minimal increase in risk; 2-5 drinks/day result in 1.5 increased risk compared with nondrinkers.
HRT, hormone replacement therapy; LCIS, lobular carcinoma in situ.

All women can benefit from these preventive measures

As primary care physicians, we have a responsibility to stress lifestyle modification as the mainstay of breast cancer prevention. Whether or not a woman is at high risk, advise her that maintaining a normal weight, exercising vigorously, limiting alcohol consumption, and breastfeeding are evidence-based methods of primary prevention. Diets low in fat and high in fiber may be associated with a lower risk of invasive breast cancer, but there is no conclusive evidence to support specific dietary interventions to reduce the risk.8-11 Nor has a link between active or passive smoking, antioxidants, or fruit and vegetable intake been firmly established.12

There is a clear association between prolonged estrogen exposure and breast cancer, however. Many reproductive factors, such as early menarche, late menopause, later age at time of first full-term pregnancy, and nulliparity, increase a woman’s exposure to endogenous estrogen—and her risk of developing breast cancer.12,13

Exposure to exogenous estrogen is also linked to the development of breast cancer. In 2002, the Women’s Health Initiative (WHI) was stopped early after a report was released stating that the risks of hormone replacement therapy (HRT)—a higher incidence of cardiovascular events, stroke, and venous thromboembolism, as well as breast cancer—outweighed the benefits.14 Subsequent analyses have found a relationship between the declining incidence of breast cancer and the marked decrease in HRT use prompted by the WHI report. While causality has not been firmly established, multiple studies strongly suggest it.15,16


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