Determining Breast Cancer Risk and Screening Methodologies
October is breast cancer awareness month. With roughly 260,000 new diagnoses of breast cancer in the U.S. in 2018, it is important for healthcare providers to be aware of a patient’s risk of developing breast cancer in order to facilitate appropriate cancer screening, surveillance, and referrals to specialists.
After hearing that one in eight women in the U.S. will develop breast cancer in their lifetime, one might assume that all women have about a 12% chance of developing breast cancer. However, this is not the case. Factors such as family history of breast cancer, mutations in genes linked to breast cancer, and environmental risk factors such as diet, exercise, and even the age a woman began her period or had her first child can influence one’s personal risk of developing breast cancer.
Breast cancer risk reduction and screening methodologies differ greatly depending on an individual’s specific risk. It is very important for a healthcare provider to understand his/her patient’s individualized risk of developing breast cancer so they can recommend the most appropriate cancer screening, with the goal of early detection and better health outcomes.
Cancer risk can be broadly broken down into three main categories: average risk, moderate or familial risk, and high or hereditary risk. One of the most useful pieces of information in determining a patient’s breast cancer risk is her family history. Many medical societies, including the American College of Obstetrics and Gynecology (ACOG) and the American Society of Clinical Oncology (ASCO), recommend healthcare providers take a complete family history to determine a patient’s genetic and familial risk factors. Knowing how many of the patient’s close relatives have had breast cancer and the ages at which they were diagnosed can help delineate a patient’s risk.
Healthcare providers can also use risk assessment models, like the Gail model or Tyrer-Cuzick to calculate breast cancer risk. These models incorporate factors like family history of breast cancer, a woman’s age, height, weight, age at menarche, personal history of breast biopsies, and personal history of benign breast disease to determine a patient’s risk of developing breast cancer within five years, 10 years, and/or in their lifetime.
Different breast cancer screening and risk reduction strategies are recommended depending on the results of the Gail and Tyrer-Cuzick risk calculators. For example, women with a greater than 1.7% five-year risk of developing breast cancer based on the Gail model should consider the use of risk reduction agents (e.g. clinical trial or Tamoxifen, Raloxifene, or Aromatase inhibitor). The National Comprehensive Cancer Network (NCCN) recommends these medications be considered by high risk women as they can reduce the risk of breast cancer by as much as 50%.
Fortunately, most women (roughly 70%) have an average lifetime risk of only about 12% for developing breast cancer. Average risk is often defined as less than a 20% lifetime chance or less than a 1.7% five-year risk of developing breast cancer. According to the NCCN, women at an average risk of developing breast cancer should have a clinical breast exam every one-to-three years beginning at age 25, and annual mammograms starting at age 40.
Those who fall into a high risk or hereditary breast cancer category have usually tested positive for a rare genetic mutation in a gene associated with a significantly increased risk breast for cancer. Only about 5-10% of cancer is linked to a hereditary cancer syndrome. For example, females with a mutation in the BRCA1 or BRCA2 genes have up to a 56-87% chance of developing breast cancer. It is recommended that these individuals consider high-risk breast cancer screening, the use of risk reducing agents (like Tamoxifen), or prophylactic bilateral mastectomies.
High-risk breast cancer screening involves annual breast mammograms with tomosynthesis, annual breast MRIs with contrast, and clinical breast exams every 6-12 months. This screening could be considered as early as age 25 in individuals with certain hereditary cancer syndromes.
It is extremely important for patients and healthcare providers to be aware that breast cancer risk is not equal among all breast cancer genes. Many of the genes, like BRCA1/BRCA2, PTEN, and TP53 are associated with significant breast cancer risks and there are specific management recommendations, including the option for prophylactic bilateral mastectomies, for people who test positive.
Other genes associated with breast cancer, like CHEK2, PALB2, and NBN, have been more recently studied to determine their risks. The risks of breast cancer vary with these other moderate risk genes, which in turn result in very different recommendations for screening and risk reducing options. For example, a woman who is BRCA1 positive may have up to a 56-87% lifetime risk of breast cancer. But a woman with a CHEK2 mutation may have a 28-37% lifetime risk.
Approximately 20-25% of women fall into a moderate or familial breast cancer risk category. These may be individuals who do not qualify for genetic testing for hereditary breast cancer syndromes or have tested negative for a hereditary breast cancer syndrome, but still have a strong family history of breast cancer. This category may also include individuals who have tested positive for mutations in genes associated with a low to moderate increased risk for breast cancer (as described above).
The NCCN recommends women in this moderate breast cancer risk category have clinical breast exams every 6-12 months, annual screening mammograms beginning 10 years prior to the earliest breast cancer diagnosis in the family, but not before age 30 or after age 40. In addition, it is recommended that annual breast MRIs be conducted, beginning 10 years prior to the earliest breast cancer in the family but not before age 25.
Understanding the complicated interplay of genetics, family history, and environmental factors on breast cancer risk can be challenging, but is crucial in understanding a person’s chance of developing breast cancer. Due to the complexity of hereditary cancer genetic test results, many professional medical societies recommend speaking to a genetics expert about cancer risk, options for genetic testing, and genetic test results both before and after genetic testing. Genetic counseling can be very beneficial in determining one’s personalized risk for breast cancer with the goal of early detection and prevention. For more information about genetic counseling, visit the National Society of Genetic Counselors web site: www.nsgc.org. Genetic counseling via phone and video is available from InformedDNA when ordered by a healthcare provider.
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