Thursday, November 25, 2010

Breast cancer screening for women in their forties

Breast cancer screening for women in their forties has become a hot topic recently because some scientists have argued that the harms outweigh the benefits. A recent article in the journal Science (Marshall, Brawling over mammography, 2010) discusses this issue and presents some scientist's points against screening.

I wrote a letter to the journal describing how the benefits of x-ray mammography add up to a substantial number of breast cancer deaths avoided. Although we don't know the true number of lives the technology saves, I point out that if we had pervasively available screening and all women volunteered for the program at the appropriate period of their lives then the total number of deaths averted is quite substantial. I just found out that the letter got published and since Science did not take out a copyright on my letter I am reproducing it here: (you can also access the letter directly off of their website here)

Mortality, Anxiety, and Politics in Breast Cancer Screening for Women Aged 40 to 50

In the News Focus "Brawling over mammography" (E. Marshall, 19 February 2010, p.936), arguments are presented by prominent scientists for and against x-ray mammography-based breast cancer screening for women aged 40 to 50. The main argument against x-ray mammography screening is that it saves few lives, and its harms (such as unnecessary surgeries and increased patient anxiety) are substantial. Opponents of breast cancer screening for women in their forties should take note of some simple statistics and their profound implications for politicians and society. Marshall's story highlights a study by Heidi Nelson indicating that we need to screen 1904 women in their forties to prevent one death from breast cancer. While it is true that we have to screen many women in order to prevent one breast cancer death, consider the United States' female population of about 157.5 million. If fully developed x-ray mammogram screening programs were available to all U.S. females, and they were to volunteer for the program during their forties, based on Nelson's numbers over 82,000 breast cancer deaths would be prevented in the Unites States (157.5 million / 1904 screened to prevent one breast cancer death).

Scientists who argue against the use of mammography for women in their forties should consider how politically and morally unacceptable the elimination of this screening would be. No politician would support the elimination of x-ray mammography screening given the total number of lives that are at stake when we consider mammography's effect on society as a whole.

Additionally, Marshall points out that some opponents of x-ray mammographic screening for women in their forties rightfully state that a false positive diagnosis from a mammogram is sure to cause the patient substantial anxiety. Patient anxiety is difficult to measure. Although it should not be dismissed, the anxiety of patients receiving false positive diagnoses and unnecessary surgery after mammographic screening does not necessarily outweigh the alternative anxiety of a population of women that aren't screened but worry about their lives.

Jacob Levman
Sunnybrook Research Institute
University of Toronto