Results from a major Canadian study show that yearly mammograms combined with physical breast examination for women 5059 years old who were also trained to perform breast self-examination does not lower breast cancer mortality compared with yearly physical examination alone.
Dr. Anthony Miller of the University of Toronto and colleagues, reporting for the Canadian National Breast Screening Study-2, present their results in the September 20 issue of the Journal of the National Cancer Institute. They note that mammography in combination with physical breast examination detected more lymph-node negative and more small breast cancers than physical examination alone. However, after 13 years of follow-up, breast cancer deaths were practically identical in the two groups.
The study involved 15 screening centers in six Canadian provinces. From January 1980 through March 1985, study entrants were randomly assigned to one of the two arms of the study19,711 women to the arm receiving mammograms and physical breast examinations, and 19,694 women to the physical examination-only arm. All women were carefully trained to perform breast self-examinations. The women were followed from entry for an average of 13 years.
Five annual screening examinations were offered to the first 62% of the women entering the study and four to the remainder. Nurses carried out the physical examinations in 12 of the 15 screening centers, and physicians performed the examinations in the other three. The examination, both physical and visual, took about 10 minutes. Two-view film-screen mammography was used at all screening centers, and a stratified random sample of all films was systematically reviewed by a single reference radiologist. Women with suspicious physical or mammographic findings were assessed by study surgeons who made appropriate recommendations to the family physicians.
Over the screening period and subsequent follow-up period, 622 invasive breast cancers were detected in the mammography plus physical examination group, compared with 610 in the physical examination-only group. Linkage of study participants to the Canadian Mortality Data Base showed that through 1993 there were 88 deaths from breast cancer in the mammography plus physical examination arm and 90 breast cancer deaths in the physical examination-only arm. These results show that mammography was not associated with a reduction in breast cancer deaths even though mammography detected smaller cancers than physical examination did.
The authors conclude that, for women older than 50 years, thorough annual physical breast examinations, plus teaching of breast self-examination, may be a useful alternative to mammography. The authors emphasize that physical examinations for screening involve far more skilled attention to relatively minor signs than those often rather casually performed by health-care workers who have not been trained to recognize the subtle physical signs of early breast cancer.
Contact: Megan Easton, University of Toronto, (416) 978-5948; fax: (416) 978-1632.