Breast Cancer Screening Lowers Mortality, Yet Questions Remain

By ACSH Staff — Jan 12, 2016
When should women at average risk for breast cancer start mammography screenings? Should they start at 40, or is it better to wait until 50? The U.S. Preventive Services Task Force has weighed in, concluding that "cancer mortality is generally reduced" with screening. But other issues need answers.

images-1There are few medical decisions that have been more contentious than those surrounding screening for breast cancer. Whether it's the age of initiation, frequency of screening (via mammography), or if or when to stop screening, various health organizations differ in their recommendations, leaving women confused, and some, frightened.

Now the U.S. Preventive Services Task Force has just released its latest guidelines, which will supersede all previous ones from that organization. The USPSTF "makes recommendations about the effectiveness of specific preventive care services for patients without related signs or symptoms. It bases its recommendations on the evidence of both the benefits and harms of the service, and an assessment of the balance. The USPSTF does not consider the costs of providing a service in this assessment."

As examples of the conflicting recommendations, the latest guidelines from the American Cancer Society suggest that women at average risk for breast cancer begin annual screening at age 45, perhaps changing to biennial (every other year) screening after age 55. In addition, the ACS suggests that women as young as 40 be allowed to begin screening if they opt to do so. On the other hand, the The National Comprehensive Cancer Network (NCCN) recommends routine mammography for women starting at age 40. Susan G. Komen "For the Cure" merely presents the various organizations' recommendations without pointing to any one of them specifically.

There is a graded strength which the USPSTF provides for each service it recommends:

  • A: The service is recommended as there is high certainty that there is a substantial net benefit
  • B: The service is recommended, with a high certainty that the net benefit is moderate or moderate to substantial
  • C: The service should be selectively offered or provided, based on professional judgement and patient preference; the net benefit is moderately certain to be small
  • D: The service is not recommended, since there is moderate or high certainty that there's no net benefit of the service, or the harms outweigh the benefits
  • I: There is insufficient evidence to assess the balance of harms and benefits of the service; evidence is lacking, of poor quality or conflicting

For breast cancer screening the USPSTF evaluated 38 studies, including five systematic reviews of 62 individual studies. The USPSTF report, whose first author is Dr. Heidi D. Nelson of Oregon Health & Science University in Portland, examined whether screening women at average risk, at different ages made a difference in terms of their mortality and the occurrence of advanced breast cancer. Overall, the research found that:

"Breast cancer mortality is generally reduced with mammography screening, although estimates are not statistically significant at all ages and the magnitudes of effect are small. Advanced cancer is reduced with screening for women aged 50 years or older."

Because of these results, the USPSTF made the following recommendations for women at average risk of breast cancer (that is, for women who do not have family histories, or a gene mutation known to increase risk):

  • For women aged 40-49: The decision to screen should be an individual one, and should be based on the preferences of the individual in consultation with her health care provider (USPSTF grade C)
  • For women aged 50-74: Screen every two years (USPSTF grade B)
  • For women 75 and older: No recommendation (USPSTF grade I)

The most disputed recommendation is still what the 40-49 year-old woman at average risk of breast cancer should do. Based on its own grading system, the USPSTF indicates that the recommendation or provision of screening of these women is likely to provide only a small benefit however, the group doesn't recommend against screening for this group.

As more data are provided by future research, one can only hope that these ambiguities in the recommendations and disagreements between various organizations are clarified and rectified.