| A new study conducted by the National
Breast Screening Study of Canada (NBSS) finds the number of deaths from breast cancer is nearly equal among women in their fifties,
regardless of whether women have annual screening mammograms
or simply have annual physician-performed clinical breast
exams. The study contradicts previous studies, which show that annual screening
mammography is responsible for a decrease in breast cancer deaths. In the NBSS study, researchers followed nearly
40,000 women between the ages of 50 and 59 from 1980 to 1993. The women were divided into
two groups: group #1 underwent yearly screening mammograms and clinical breast exams,
while group #2 only had yearly clinical breast exams. All of the women in the study were
taught how to perform monthly breast self-exams.
The results of the study show that the
number of deaths from breast cancer was approximately the same among the two groups of
women. Among the women who had screening mammograms in addition to clinical breast exams,
622 women were diagnosed with invasive breast cancer and 107 women died of breast cancer.
Among the women who only had clinical breast exams, 610 were diagnosed with invasive
breast cancer and 105 women died of breast cancer. Thus, the Anthony Miller and his
colleagues conclude that "the addition of annual mammography screening to physical
examination has no impact on breast cancer mortality" among women aged 50 to 59.
The Canadian study, which appears in
the September 20, 2000 issue of the Journal of the National Cancer Institute is
raising concerns from national breast cancer organizations and physicians. According to a
press release by the Susan G. Komen Foundation, "as with all forms of clinical study,
one study is not enough to change public health policy."
"Women need to continue to
practice three steps to early detection," said Rebecca Garcia, PhD, vice president of
the Komen Foundation, in a press release. Those three steps (for all women 40 years of age
and older) are monthly breast self-exams, yearly clinical breast exams, and yearly
screening mammograms. "While not perfect, mammography is the best known screening
tool widely available today," said Dr. Garcia.
Physicians Find Fault with the Study
Other physicians are questioning the
design and execution of the Canadian study. In a guest editorial for Oncology.com, Daniel
Kopans, MD, director of breast imaging at Massachusetts General Hospital, cites several
potential inaccuracies with the NBSS study. According to Dr. Kopans, since the study
involved volunteers, it cannot be used to assess the general population. In the study, the
death rate of 17% among the women who only received clinical breast exams over 10 years is
extremely low.
Dr. Kopans and other physicians also
argue that the quality of screening mammograms received by the women in the study was
poor. The image quality was low, the radiologists interpreting the mammograms may not have
received specialty training, and the mammography screening as a whole was "far below
state-of-the-art" even for the time period (1980s). Furthermore, the clinical breast
exams performed by physicians in the study were extremely thorough and lasted between 10
to 15 minutes each. Clinical breast exams performed in the average doctor’s office
tend to last only one a minute or two.
While the results of the study show
that clinical breast exams can play a significant role in breast cancer detection, the
American Cancer Society, the American College of Radiology, the American College of
Surgeons and the American Medical Association all recommend that women supplement physical
exams with annual mammograms once they reach 40 years of age.
Guidelines for early breast cancer
detection:
- All women between 20 and 39 years of age
should practice monthly breast self-exams and have a physician performed clinical breast
exam at least every three years.
- All women 40 years of age and older
should have annual screening mammograms, practice monthly breast self-exams, and have
yearly clinical breast exams.
- Women with a family history of breast
cancer or those who test positive for the BRCA1 (breast
cancer gene 1) or BRCA2 (breast cancer gene 2) mutations
may want to talk to their physicians about beginning annual screening mammograms earlier
than age 40, as early as age 25 in some cases.
Interestingly, a recent study released by the Institute of Cancer Research finds
a significant decrease (21%) in breast cancer deaths in England and Wales during the
1990s. The researchers attribute this decline in breast cancer deaths to improved
treatments and a national mammography screening program that was implemented in the late
1980s.
Additional Resources and References
- The medical study, "Canadian
National Breast Screening Study-2: 13-Year Results of a Randomized Trial in Women Aged
50-59 Years," is published in the September 20, 2000 issue of the Journal of the
National Cancer Institute. An abstract of the study is available at http://jnci.oupjournals.org/cgi/content/abstract/92/18/1490
- The September 20, 2000 Komen press
release, "The Susan G. Komen Breast Cancer Foundation Finds Canadian Mammography
Study Enlightening, Underscores Need for Continued Research," is available at http://www.breastcancerinfo.com/news/html/092000.asp
- The September 19, 2000 editorial by
Daniel Kopans, MD, "National Breast Screening Study of Canada: Study Design,
Mammogram Quality Cause for Concern," is available on Oncology.com at http://www.oncology.com/v2_MainFrame/1,1614,_12|00263|0
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