Mammograms for Young BRCA Mutation Carriers
New Research Highlights Importance of Breast Self Exam
At the annual meeting of the American Society of Breast Surgeons, Duke University researchers demonstrated that breast self-exam (BSE) can detect new breast cancer in high-risk women, stating, “Our results provide evidence that BSE should not be abandoned as an adjunct for breast cancer education, as well as a surveillance tool for high-risk women.”
L. Wilke, V Seewaldt, et. al. Breast Self- Examination: Defining a Cohort Still in Need. Presented as a poster at American Society of Breast Surgeons annual meeting, April 2009.
Calculating the Risks and Benefits
by Dr. Margaret Snow and Sue Friedman
A new study affirms the benefits of mammograms for BRCA carriers over age 30, but raises questions about relative risks versus benefits for younger women.
Although National Comprehensive Cancer Network (NCCN) guidelines recommend BRCA carriers begin mammography at age 25, some experts have concerns that starting mammograms before age 30 means a higher lifetime exposure to radiation and increased breast cancer risk. Because breast cancer is uncommon in younger women—even those who have a BRCA mutation—mammography detects fewer cancers in high-risk women in this age group; thus fewer cancer deaths are prevented by starting mammograms at this young age. Additionally, because mammography frequently fails to detect cancers in the typically dense breast tissue of younger women, whether the benefit of early mammograms offsets the risk of additional radiation exposure is unclear. Study authors noted that no direct research has compared the benefits and risks of mammogram screening for women younger than 40.
Exactly how much cancer risk is increased when mammograms begin before age 30 is unknown. Using data from research specific to BRCA carriers and other studies of non-BRCA carriers exposed to radiation, the study authors estimated the risk of radiation induced breast cancer from mammography given before and after age 30. Using mathematical models, they calculated that for every 10,000 women between ages 25-30, early mammograms would save 12 or fewer lives, while radiation delivered to those same women would cause about 51 breast cancer deaths 10 or more years later.
Among women with BRCA1 who start mammograms at ages 30-35, the models indicate screening would save more lives than would be lost to radiation-induced breast cancers (174 projected BRCA-related breast cancer deaths per 10,000 women vs 20 radiation-induced cancer deaths later in life). The models predicted similar results and the same concerns regarding the risk-benefit ratio for young BRCA2 women undergoing screening between the ages of 25-29. The risk-benefit ratio for mammograms in women older than 30 was favorable for both BRCA1 and BRCA2 carriers.
The authors observed that risk-reduction strategies such as mastectomy or oophorectomy later in life after radiation exposure alter the balance of risk-to-benefit in favor of screening. One of the researchers, Dr. Mark Robson of Memorial Sloan Kettering, reported that results of this exercise raise questions about the practice of recommending mammograms from age 25, but do not provide enough evidence to change protocols.
The researchers noted the study’s limitations, acknowledging the gaps in what we know of breast cancer and screening in young BRCA carriers, and specifically, how radiation exposure affects them. They also acknowledged that some of the model assumptions made are not universally accepted. They theorized that even very small doses of radiation cause small changes in DNA and increase the risk of cancer by a small amount, and that the combination of risk factors multiplies. Their study also relies on presumptions that survival in young women diagnosed with BRCA-related breast cancer is similar to survival of older women with sporadic breast cancer. Their model didn’t take into account the emerging theory that BRCA1 cancers may develop more quickly than sporadic cancers. According to Dr. Robson, allowing that BRCA1-related cancers develop quicker and between screenings further reduces the potential benefit of mammography in BRCA1 mutation carriers under age 30.
More needs to be known about the effectiveness of mammograms in this young age group, particularly when compared to MRI screening, which is without radiation risk. We need to identify types of breast cancers that typically occur in young women and determine the frequency of cases of DCIS, which, when missed by MRI are sometimes detected by mammogram. The answers to those questions will help determine whether mammograms should continue to be a part of screening protocols for women under 25.
Dr. Robson is already taking the next step to better determine how safe and useful mammograms are for women under age 30. He and other researchers are reviewing study data of breast cancer in young women, and early detection studies comparing MRI and mammogram. He points out that because the risk of radiation-induced cancer is small, particularly compared to the risk of BRCA-associated breast cancer, and the timeframe for radiation-induced cancers to develop would span a woman’s life, studying this question directly would require large numbers of BRCA carriers and take decades to provide answers.
Dr. Margaret Snow is a previvor and a Physical Medicine and Rehabilitation physician who enjoys golfing and photographing birds. She serves as FORCE's West Michigan Outreach Coordinator.
AB de Gonzalez, CD Berg, K Visvanathan, M Robson. Estimating risk of radiation-induced breast cancer from mammographic screening for young BRCA mutation carriers. Journal of the National Cancer Institute, 2009; 101: 205-209.
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