By Tracy Weitz, chair of Breast Cancer Action’s board of directors, Director of the Advancing New Standards in Reproductive Health program, and Associate Director for Public Policy at the National Center of Excellence in Women’s Health
[Editors’ Note: In the past few months there have been several new studies--and extensive media coverage--about mammography. Breast Cancer Action is committed to helping you understand the science behind the headlines so you have unbiased, accurate information with which to make decisions about your own health. We asked Tracy to break down the science behind breast cancer screening].
Screening mammograms are the tests performed on women with no known risk factor for breast cancer and no symptoms, such as a lump. Screening mammography is presently the best tool we have for diagnosing breast cancer in the broad population, but it is remains very limited in what it is able to promise. These limitations include: the fact that screening will never prevent breast cancer, and only detects cancer after it has occurred; that mammography misses some breast cancers; that some cancers cannot be effectively treated regardless of early detection; and finally, that, while some women’s lives will be saved by early detection of breast cancer on mammography, many women will be diagnosed with cancers that would never kill them or that can be detected later and still successfully treated. These women will be turned into cancer patients unnecessarily or prematurely, a process known as overtreatment.
Given the significant limitations of screening mammography, the core debate about breast cancer screening continues to revolve around what age women should have mammograms, and how frequently those procedures should be performed. Last month two new studies were released, both of which provided additional support for BCAction’s long-standing and cautionary position on screening mammography for women at normal risk.1
- “Likelihood That a Woman with Screen-Detected Breast Cancer Has Had Her “Life Saved” by That Screening.” H. Gilbert Welch, MD, MPH; Brittney A. Frankel. Archives of Internal Medicine: October 24, 2011.
- “Cumulative Probability of False-Positive Recall or Biopsy Recommendation After 10 Years of Screening Mammography A Cohort Study.” Rebecca A. Hubbard, PhD; Karla Kerlikowske, MD; Chris I. Flowers, MD; Bonnie C. Yankaskas, PhD; Weiwei Zhu, MS; and Diana L. Miglioretti, PhD. Annals of Internal Medicine: October 18, 2011.
The first study, authored by Dr. Gilbert Welch of Dartmouth University, addresses the question of whether women’s lives were saved when their breast cancer was detected by mammography. By looking at probabilities of breast cancer detection for the general population in the United States, the study found that for 50 year-old women, 13 percent of lives were saved by finding the breast cancer through a mammogram. This means that the majority—or 87 percent—of women whose breast cancer was found through mammography did not have their lives saved by screening.
In part, the study suggests that the cancers of these women would have been equally treatable if it had presented clinically. However, more troubling is the suggestion that the cancer never needed to be treated. Challenging the common narrative that every woman whose breast cancer was detected by mammogram has had her “life saved” because of screening, the study concludes: “Our analyses suggest this is an exaggeration. In fact, a woman with screen-detected cancer is considerably more likely not to have benefited from screening.”
The second study, authored by Dr. Rebecca Hubbard of the Group Health Center for Health Studies in Seattle, Washington, examines the risks of false positive findings and subsequent biopsies from mammography. The study found that 61 percent of women in their 40s who had annual mammograms over a 10-year period would have a false positive result when disease was not present. Of those who underwent screening every other year, 42 percent had at least one false positive result. The probability of having a false-positive biopsy recommendation was 7 percent with annual screening and 5 percent with every-other-year screening.
Given these new findings, why do so many professional medical groups and cancer advocacy organizations continue to push for more frequent mammograms? To answer this question, we must remember that the risks and benefits of screening are weighted differently, depending on one’s vantage point. For example, physician groups who may be most concerned with limiting medical liability will opt for more frequent screening in an effort to avoid malpractice suits over possible missed cancers. Higher rates of false positives and greater rates of overtreatment have no direct cost to these physicians as these are burdens borne by patients. Other physician groups gain direct financial benefit from more follow-up tests and more diagnoses of disease.
Similarly, advocacy groups which are financially supported by companies that make a profit from breast cancer treatments benefit from the large number of women who believe that early detection saved their lives, even when diagnosis and treatment were unnecessary. This is the primary reason that BCAction takes no direct contributions from entities that benefit from cancer.
The two studies released in October 2011 provide further evidence for what BCAction has always encouraged–women should weigh the risks and benefits of mammography and make their own decision on timing and frequency of screening. BCAction continues to stand by our recommendations, which follows the science and puts patients at the center of the cost/benefit analysis.
BCAction takes no money from pharmaceutical companies or any other company that profits from or contributes to the cause of cancer. That is why they rely on the support of individuals like you. Please make your year-end donation today.
The Source—Fall/Winter 2011 | 12.14.11© 2011, Breast Cancer Action ISSN #1993-2408, published quarterly by BCAction. Articles on detection and treatment do not constitute endorsements or medical advice but are intended solely to inform. Requested annual donation is $50, but no one is refused for lack of funds. “Breast Cancer Action”, “Think Before You Pink” and the BCAction logo are the registered trademarks of Breast Cancer Action. All rights reserved. Not to be used without express written permission.