Commentaries question benefit of early breast cancer screening

A series of three commentaries in the October 15 issue of the Journal of the National Cancer Institute address the issue of whether premenopausal women are being accurately informed about the potential harms versus benefits of mammography before undergoing screening.

In the first commentary, Cornelia J. Baines, M.D., of the University of Toronto, notes that randomized trials of breast cancer screening have consistently found that for women ages 40 to 49, screened women have a higher rate of death from breast cancer than unscreened women for up to 11 years after screening starts--only then do benefits appear.

"Women are supposed to be informed before making decisions about screening, but unfortunately, most are ill-informed about both the hazards and the benefits of screening," Baines writes.

She offers possible biologic explanations for the higher mortality rates among younger women treated for breast cancer, such as the stimulation of dormant metastases after surgery and the low-energy x-rays used in screening mammography, which some believe are more likely to cause cancer than high-energy x-rays.

Baines says more concrete answers should be available after publication of results from a U.K. trial of mammography screening, which recruited women as they turned 40 years old.

In a counterpoint to the commentary, Alfred O. Berg, M.D., writing on behalf of the U.S. Preventive Services Task Force, points out that the evidence suggesting an early mortality increase is weak and its real importance is unknown.

Still, he cautions, screening in premenopausal women may have important harms, including false-positive results, unnecessary biopsies, and possible overdiagnosis and overtreatment of cases that might not have been clinically important.

"Thus, whether screening actually reduces survival for a very small number of younger women may or may not outweigh the value women place on the benefit of the modest reduction in long-term risk and the much higher likelihood of less serious, but nonetheless important, harms," says Berg, of the University of Washington, Seattle.

Baines agrees with this latter point, adding that she hopes the commentaries will prompt others to investigate the causes of the puzzling observation. In the meantime, she says, "women should carefully consider whether screening is the right choice for them. They cannot do that until they are completely informed."

Contact: Janet Wong, University of Toronto, 416-978-5949, fax: 416-978-7430, jf.wong@utoronto.ca; Pam Sowers, University of Washington, 206-543-3620; fax: 206-616-9080, sowerspl@u.washington.edu.

Baines CJ. Mammography screening: Are women really giving informed consent? J Natl Cancer Inst 2003;95:1508–11.

Berg AO. Mammography screening: Are women really giving informed consent? (Counterpoint) J Natl Cancer Inst 2003;95:1511–12.

Baines CJ. Mammography screening: Are women really giving informed consent? (Countering the Counterpoint) J Natl Cancer Inst 2003;95:1512–13.

Note: The Journal of the National Cancer Institute is published by Oxford University Press and is not affiliated with the National Cancer Institute. Attribution to the Journal of the National Cancer Institute is requested in all news coverage.

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