A new study conducted by the National Breast Screening Study of Canada Controversial Study Finds Clinical Exams Equal to Mammography With Respect to Breast Cancer Mortality For Women in Their Fifties (dateline October 2, 2000) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Controversial Study Finds Clinical Exams Equal to Mammography With Respect to Breast Cancer Mortality For Women in Their Fifties (dateline October 2, 2000)

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.

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