Independent Task Force Updates Recommendations on Breast Cancer Screening
Yesterday, the United States Preventive Services Task Force (USPSTF) updated recommendations on breast cancer screening, suggesting that women ages 50 to 74 who are at average risk for getting the disease undergo a routine screening mammogram every 2 years. The recommendations were published in the November 17 Annals of Internal Medicine.
“When women are screened every other year instead of every year, you see a large reduction in the harms caused by false-positive screening results, and the reduction in breast cancer mortality remains high—between 70 and 99 percent of what you see with annual screening,” explained Dr. Diana Petitti, vice chair of the USPSTF committee that issued the recommendations. False-positive screening results can cause harms including unnecessary biopsies and emotional distress.
The USPSTF is a panel of independent primary care physicians from around the country that periodically reviews the evidence for preventive health services, including screening, medication, and counseling. The panel’s earlier recommendations for breast cancer screening, last updated in 2002, advised mammography with or without clinical breast exam every 1 to 2 years for women ages 40 and older.
Updated recommendations suggest that women ages 50 to 74 who are at average risk for breast cancer undergo a routine screening mammogram every 2 years.
The new recommendations do not advise routine mammography for average-risk women ages 40 to 49. Instead, they advocate for “individualized informed decision making based on specific benefits and harms for women who consider screening before age 50 years,” noted Dr. Karla Kerlikowske of the San Francisco Veterans Affairs Medical Center in an accompanying editorial.
The updated 2009 recommendations also advise against teaching breast self-exam (BSE). The 2002 recommendations did not advise either for or against teaching BSE, but because no clinical trials to date have shown that widespread teaching of the technique reduces the number of deaths from breast cancer, the task force now recommends against systematic teaching of BSE.
However, explained Dr. Stephen Taplin, senior scientist in NCI’s Division of Cancer Control and Population Sciences’ Applied Research Program (ARP), a recommendation against routine teaching of BSE “certainly does not mean that women shouldn’t respond to lumps and bumps or other troublesome changes in their breasts that they discover on their own. Women should go to their health care provider when they have a concern.”
NCI and Breast Cancer Screening Research
Many questions about breast cancer screening remain unanswered, such as:
- What are the relative benefits and harms of mammography for women ages 75 and older?
- Why are interval breast cancers (tumors that are found in between scheduled screening examinations) often more aggressive and deadly?
- Why do some breast cancers progress quickly while others do not, and can some individual tumors regress even without treatment?
- Can gene or protein expression patterns of a tumor predict its aggressiveness?
NCI is currently funding many large-scale research projects addressing these questions, including:
The task force based the updated recommendations, in part, on two commissioned evidence reports that synthesized data that had accumulated since the USPSTF’s last revision 7 years ago. One of these was performed by the Oregon Evidence-based Practice Center (EPC) at Oregon Health and Science University and was intended to find and summarize all the high-quality, pertinent studies that could help answer the questions about optimizing breast cancer screening.
To this end, the EPC reviewed new studies and new data from published trials of screening mammography that had been reviewed by the task force in 2002, including the Age trial from the United Kingdom, the only clinical trial to specifically evaluate the effectiveness of screening mammography in women in their 40s. This set of data allowed the task force to more precisely estimate the reduction in deaths from breast cancer with mammography in this age group.
The EPC also analyzed data on more than 600,000 women ages 40 or older that had been collected by the Breast Cancer Surveillance Consortium. These data indicated that false-positive results on a mammogram are most common among women ages 40 to 49.
The second evidence report was prepared by NCI-funded members of the Cancer Intervention and Surveillance Modeling Network (CISNET). For this new study of mammography, six modeling teams examined the hypothetical outcomes of 20 different mammography screening strategies that differed in the ages when screening began and ended and in the number of years between scheduled screenings.
The models developed by these teams showed that screening every other year produced an average of 81 percent of the mortality reduction of yearly screening, but with nearly 50 percent fewer false-positive results. Screening women ages 50 to 69 every other year would provide a median reduction in breast cancer mortality of 16.5 percent compared with no screening. When compared with screening from ages 50 to 69, beginning screening every other year at age 40 produced a small additional reduction in mortality but increased the number of false-positive results by more than 50 percent.
“Everything about breast cancer screening is a trade-off, within the ages for which it has been shown to be beneficial,” explained Dr. Petitti. “All of these lines of evidence indicate that women ages 40 to 49 would have a small improvement in breast cancer mortality but also a large set of harms related to false-positive results.”
“It is important for women to understand that these results come from analyses of women who were drawn from the general U.S. population,” added Dr. Taplin, “and as such, they do not account for all variations in breast cancer risk and do not apply to women at very high risk for breast cancer.”