NBCC believes women deserve to know the truth about mammography screening, including its harms, and limitations. The unwarranted emphasis on breast cancer screening and early detection has diverted attention from the reality of breast cancer - the fact that all breast cancers are not equal and that current screening methods are not significantly reducing the toll from lethal breast cancers. The focus must change from the cancers that will not kill to those that do. For more than a decade, NBCC has taken the position that mammography screening has significant limitations and should be a personal choice rather than a public health message. We have analyzed the seven prospective clinical studies that have investigated the issue and the analyses and reviews that have followed. For example:
A 2002 systematic review for the U.S. Preventive Services Task Force found a 15% relative reduction in risk for women between the ages of 40-49 years that was only borderline statistically significant, and led the authors to conclude that “the absolute benefit of mammography screening on mortality is very small, and that biases in the trials could either erase or create it.”
- A 2006 Cochrane Collaboration systematic review found that screening mammography decreases the risk of death from breast cancer by about 15% in relative terms, or 0.05% in absolute terms, and that throughout a ten-year period, for every 2000 women screened, one death from breast cancer will be prevented but ten healthy women will undergo unnecessary diagnostic procedures and treatment with the attendant toxic effects.
- An analysis by the American College of Physicians found that for women in the 40-49 year age range, the risks of screening mammography outweigh the benefits.
- An analysis by Berry, et al. used statistical modeling to estimate the contribution of screening mammography to lowering the overall breast cancer mortality rate and found that the range varied too greatly to accurately assess the extent to which screening decreased the mortality rate.
- A recent article by Esserman, et al. in the October 2009 issue of JAMA continues to highlight the fact that screening mammography has not been shown to significantly decrease the number of aggressive or later-stage breast cancers.
After reviewing and analyzing these studies, NBCC continues to conclude that there is no statistically significant evidence that screening women age 40-49 years reduces mortality, and no strong evidence that it does so in women over 50 years. Read NBCC’s position paper on Mammography for Breast Cancer Screening. Women need honest information regarding the value of all medical interventions. Public health resources need to be used with certainty to improve the public’s health. The reality is that screening has not been effective. While the incidence of ductal carcinoma in situ and localized invasive breast cancer increased substantially as a result of screening programs, the incidence of regional or distant stage disease declined only slightly. There may be several reasons for this, but primarily it is because screening increases the detection of non-threatening cancers, while missing the most aggressive cancers. NBCC continues to affirm the position we have taken for over a decade. Women should make a personal decision about whether to undergo screening mammography after weighing the risks and benefits.
References
Humphrey LL, Helfand M, Chan BK, et al. Breast cancer screening: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2002 Sep 3; 137(5 Part 1):347-60. Gotzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD001877. DOI: 10.1002/14651858.CD001877.pub2. Armstrong K, Moye E, Williams S, Berlin JA, Reynolds EE. Screening mammography in women 40 to 49 years of age: a systematic review for the American College of Physicians. Ann Intern Med 2007 Apr 3; 146(7): 516-26. Berry DA, Cronin KA, Plevritis SK, Fryback DG, Clarke L, Zelen M, et al. Effect of screening and adjuvant therapy on mortality from breast cancer. N Engl J Med 353:17; Oct. 27, 2005. Esserman L, Shieh Y, Thompson I. Rethinking screening for breast cancer and prostate cancer. JAMA 2009 Oct 21; 302(15): 1685-92. |
