By Cathleen London, MD
The U.S. Preventive Services Task Force (USPSTF) recently released its 2009 update to the 2002 recommendations on breast cancer screening. Specifically, they addressed critical evidence gaps that were unresolved at the time of the 2002 recommendations, including the effectiveness of mammography in decreasing breast cancer mortality among average-risk women age 40-49 years and 70 years and older; the effectiveness of CBE and BSE in decreasing breast cancer mortality among women of any age; and harms of screening with mammography, CBE, and BSE.
In reaching their conclusion, the task force analyzed data from over 40 studies, and data collected from more than 600,000 women in the United States and 160,000 women in United Kingdom. The task force also commissioned a study that involved six separate teams of researchers analyzing the risks and benefits of 20 screening strategies.
With regards to mammography, the task force concluded that “there is convincing evidence that screening with film mammography reduces breast cancer mortality, with a greater absolute reduction for women aged 50 to 74 years than for women aged 40 to 49 years. The strongest evidence for the greatest benefit is among women aged 60 to 69 years. Among women 75 years or older, evidence of benefits of mammography is lacking.”
Consistent with the 2002 recommendations, they recommended biennial screening, but based on the new analysis recommended that the screening start at age 50 and cease at age 75 in women who are not at increased risk for breast cancer by virtue of a known underlying genetic mutation or a history of chest radiation.
As physicians, it is always difficult to do less than to do more and not unexpected there has been quite a commotion regarding the new guidelines. But we have to remember that increased testing can lead to harm. In the case of earlier routine screening, the harms include: radiation exposure; pain during procedures; patient anxiety and other psychological responses; consequences of false-positive and false-negative tests; and overdiagnosis.
Overdiagnosis refers to women receiving a diagnosis of invasive or noninvasive breast cancer (i.e. DCIS and LCIS) who had abnormal lesions that were unlikely to become clinically evident during their lifetimes in the absence of screening.
The data indicate that false-positive mammography results are common in all age groups. The rate is highest among women age 40-49 years (97.8 per 1,000 women per screening round) and declines with each subsequent age decade. Rates of additional imaging are highest among women age 40-49 years (84.3 per 1,000 women per screening round). There is concern that high cumulative doses of low energy radiation may induce more cancers in younger women.
Not anticipated by the task force was how politicized their recommendations have become. The task force was unaware that the new guidelines would become distorted into a negative message. Perhaps this was naïve to expect this report to be received neutrally but the task force was created to be insulated from politics.
The task force was formed in 1984, at a time when screening methods for cancer, cholesterol levels and diabetes were just emerging and rarely paid for by insurers. The idea was to identify medical experts who could objectively evaluate evidence and to protect the group from any political pressures so they could write honest assessments. The United States Preventive Services Task Force is financed by the Department of Health and Human Services but works at a distance from it, making its decisions without consulting the agency.
“Panel members said politics and questions of cost were never part of their discussions of the risks and benefits of mammograms — in fact they are prohibited from considering costs when they make guidelines. It was the scientific evidence, they said, that led them to conclude that women in their 40s should carefully consider whether they want to be screened rather than assuming they should start screening then. And it was the evidence, they said, that led them to conclude that screening every other year provides all the benefits of screening annually.”
This is not radically different than the recommendation the 2002 panel (different member composition) stated in giving very weak recommendations for beginning screening at age 40 – though interpreted by Congress at the time as a strong endorsement for earlier screening. Ironically, for all the accusations that the new guidelines represent cost cutting strategies of the Obama administration, the current 16 member task force was appointed and seated during the Bush administration.
Mammography is not very helpful in preventing breast cancer deaths. Current estimates are that it reduces the death rate by 15 percent. Furthermore it often leads to false positives, radiation exposure from additional testing, unnecessary biopsies and, most importantly, overdiagnosis and/or over treatment. Our goals should be to better understand the biology of breast cancer development and the use of newer diagnostic modalities. Only then can we hope to save women’s lives.
Cathleen London, MD is a graduate of Yale Medical School. Board certified in Family Medicine, she runs a primary care practice and is a clinical instructor at Boston University and Tufts school of medicine and can be reached at email@example.com.
- Screening for Breast Cancer: Systematic Evidence Review Update for the U. S. Preventive Services Task Force Evidence Review Update Number 74 AHRQ Publication No. 10-05142-EF-1 November 2009
- USPSTF Screening for Breast Cancer: U.S. Preventive Services Task Force Recommendation Statement Annals of Internal Medicine Vol 151 No 10 p 716-726
- Kolata, Gina Mammogram Debate Took Group by Surprise NYT November 20, 2009