Do We Need Mammograms for Breast Cancer Screening?

The available evidence does not support the use of universal screening for breast cancer with mammography, according to the findings of an intervention review conducted by the Cochrane Breast Cancer Group.¹
   
Many studies have estimated the benefits and harms of mammography screening for breast cancer, and national recommendations vary. National guidelines suggest that for women at average risk for breast cancer, universal annual or biennial mammography screening should begin at age 40 except those issued by the U.S. Preventive Services Task Force, which recommend informed decision making with a health care provider for women aged 40 to 49 years.² To better understand the effect of mammographic breast cancer screening on mortality and morbidity, the researchers evaluated eligible trials that compared mammographic screening with no mammographic screening. A total of 7 trials that included 600,000 women aged 39 to 74 were included in the analysis.
   
No significant reduction in breast cancer mortality at 13 years was found when 3 trials with adequate randomization were analyzed (relative risk [RR], 0.90). However, a significant reduction in breast cancer mortality was found in the analysis of data from 4 trials with suboptimal randomization (RR, 0.75). Overall, the RR of breast cancer mortality was 0.81 when data for all 7 trials were combined.
   
“Breast cancer mortality was an unreliable outcome that was biased in favor of screening, mainly because of differential misclassification of cause of death,” reported the researchers.¹ According to data from the trials with adequate randomization, screening had no effect on total cancer mortality at 10 years, including breast cancer, or on all-cause mortality after 13 years.
   
Compared with women with no screening, women in the screening groups had significantly higher numbers of lumpectomies (RR, 1.31) and mastectomies (RR, 1.20). Although there was no difference between groups in the use of chemotherapy, mammography screening was associated with higher rates of radiotherapy.
   
The researchers found that with the assumption that screening reduces breast cancer mortality by 15% and overdiagnosis and overtreatment is 30%, for every 2000 women screened throughout 10 years, 1 will avoid dying from breast cancer and 10 healthy women will be unnecessarily treated. In addition, more than 200 women will undergo years of psychological distress and anxiety because of false-positive findings.
   
The researchers suggest that recommendations for the universal screening of breast cancer with mammography be reassessed and that the harms and benefits be explained to all women invited to screening.

Pertinent Points:
- Mammography screening for breast cancer was not associated with a reduction in breast cancer mortality.
- Universal screening for breast cancer with mammography may cause more harm than good among women at average risk for breast cancer.
 

References:

1. Gotzsche PC, Jorgensen KJ. Screening for breast cancer with mammography. Cochrane Database Syst Rev. 2013;6:CD001877. DOI: 10.1002/14651858.CD001877.pub5.
2. Susan G. Komen Web site. Breast cancer screening recommendations for women at average risk. Updated August 2, 2013. Available at: http://ww5.komen.org/BreastCancer/GeneralRecommendations.html. Accessed August 9, 2013.