Primary care physicians should use proven risk estimation models, genetic counseling, and other tools to identify high-risk patients, and then engage patients in shared decision making to identify the best options for prevention.
During the “Breast Cancer Prevention in Primary Care” session presented at the 2013 Pri-Med East Conference and Exhibition, Karen Carlson, MD, Massachusetts General Hospital and Harvard Medical School, discussed primary prevention and early detection of breast cancer in the primary care setting, covering: prediction of risk, identification of women at highest risk, risk-based screening, and lifestyle, supplements, and chemoprevention.
She noted that risk factors are of two types: fixed (eg, genes, age, family history, race, ethnicity, mammographic density) and modifiable (eg, body mass index, exercise, alcohol intake, hormones). She also noted that there is a difference in the ‘potency’ of risk factors—the BRCA gene is the most potent and family history is the least potent risk factor.
Carlson said that the task of the primary care physician (PCP) is to identify the women at the highest risk, as they can benefit the most from prevention and treatment. She advised PCPs to refer genetic cases for genetic testing/counseling; and for the other cases to use counseling for modifiable risk factors, to use the risk level to guide screening, and to consider chemoprevention.
Carlson advised using the Gail Model to estimate the risk of getting breast cancer. The model estimates the risk of breast cancer over the next five years and until age 90. It incorporates: age, menarche, number of first degree relatives with breast cancer, number of previous breast biopsies, presence of atypical ductal hyperplasia on a biopsy and race. She then displayed two examples of using this model to estimate risk; one woman’s estimate was a 2% five year risk and a 19% lifetime risk; another woman’s estimate was a 6% five year risk and a 35% lifetime risk.
Unfortunately, the Gail Model does not incorporate breast density, a known risk factor. Carlson suggested carefully reading the text of the mammography report looking for a buried reference to breast density and add it to the decision making process. She then showed examples of four stages of breast density, noting that the heterogeneously dense example had a 2x increased risk, while the example of an extremely dense breast had a 4x increased risk. She also noted that a screening mammography can reduce breast cancer deaths by 15-22% in women 40-75% years of age. The downside is false positives (20-40%).
Carlson then touched on some additional issues related to breast cancer prevention: what to do with overdiagnosis (estimated at 11-30%), whether or not to screen women who are in their 40s (40-49 years), and whether to use an MRI for screening. She said each is a complex issue, and decisions should be based on the latest studies, government recommendations, determined risk factors, and discussions between doctor and patient to come to a shared decision. She emphasized the importance of maintaining thorough documentation.
Chemoprevention is the use of chemotherapy (tamoxifen, raloxifene) in a healthy woman to reduce the risk of breast cancer. The USPSTF (US Preventive Services Task Force) recommends shared decision making between patient and clinician if the patient is at increased risk, and recommends against chemoprevention in low-risk patients (May 2013). Carlson presented several studies (NSABP-P1, STAR) that showed the protection provided after five years of treatment: tamoxifen reduced the risk by 50%, raloxifene by 38%. Tamoxifen’s protection continued for an additional 10 years after treatment. Both had risks (eg, uterine cancer, hot flashes), so a risk/benefit assessment is appropriate.
So, what can PCPs do to reduce breast cancer risk? Carlson recommended advising patients to: maintain a normal body weight (especially after menopause), exercise regularly, and eat a healthy diet (and limit alcohol consumption). Clinicians should also use the Gail Model to assess risk. And consider using chemoprevention for selected patients.