Breast Cancer Screening

By Graham McMahon

The latest article in our Clinical Practice series reviews current recommendations for breast-cancer screening and thesupporting evidence, including the controversy regarding mammographic screening of women in their 40s.
Worldwide, breast cancer is now the most common cancer diagnosed in women and is the leading cause of deaths from cancer among women, with approximately 1.3 million new cases and 458,000 deaths reported in 2008.OK

Clinical Pearls

 How have the screening recommendations from the U.S. Preventive Services Task Force (USPSTF) changed in recent years?
In contrast to its 2002 guidelines, the more recent recommendations of the USPSTF, published in November 2009, support a reduction in the use of screening mammography. The two most controversial changes were the reclassification of screening for women between the ages of 40 and 49 years from a B recommendation (based on moderately strong evidence) to a C recommendation (“the decision . . . should be an individual one and take into account patient context, including the patient’s values regarding specific benefits and harms”), and the recommendation that the frequency of screening be reduced from every 1 to 2 years to every 2 years.
 What is the consensus recommendation regarding mammographic screening for women between the ages of 50 and 69?
Screening mammography for women 50 to 69 years of age is universally recommended. All but one of the trials that included women in their 60s showed a significant reduction in mortality in the screened group, although this was not true for the subgroup of women in their 50s. Still, a meta-analysis revealed significant reductions in the number of deaths in both these age groups — 14% for women in their 50s and 32% for those in their 60s.

Morning Report Questions

Q: For a 42-year-old woman with no risk factors, what are the benefits and risks of screening mammography?
A: Her chance of having invasive breast cancer over the next 8 years is about 1 in 80, and her chance of dying from it is about 1 in 400. Biennial mammographic screening will detect two out of three cancers in women her age and will reduce her risk of death from breast cancer by 15%. However, there is about a 40% chance that she will be called back for further imaging tests and a 3% chance that she will undergo biopsy, with a benign finding.
Q: What are the benefits of digital mammography?
A: The contrast between breast tumors and surrounding normal parenchyma is greater with digital mammography than with film mammography, particularly when the breast tissue is dense. In one study in which almost 50,000 asymptomatic women 40 years of age or older underwent both digital and film mammography, the two techniques were equivalent overall in sensitivity (70% and 66%, respectively) and specificity (92% for both). However, in women under the age of 50 years, digital mammography was significantly more sensitive than film (78% vs. 51%).
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