Three important components of breast self examination (BSE) appear to be associated with a reduced risk of dying from breast cancer, according to results of a study published in the Nov. 1 issue of The Canadian Medical Association Journal.
"Although we're far from conclusively knowing if there is a benefit to BSE, the results of our study suggest performing specific components of BSE may lower a woman's risk of dying from breast cancer," says the study's principal investigator, Dr. Bart Harvey, an assistant professor in the department of public health sciences at the University of Toronto and associate medical officer of health in East York.
Three components of BSE appear to be associated with a reduced risk of dying from breast cancer: visually examining the breast, using the finger pads to examine the breast and using three middle fingers to examine the breast.
Women who left out one of these components in their BSE technique were almost twice as likely to die from breast cancer or to have distant metastatic disease compared to women who included all three components. Leaving out two of the three components more than doubled the odds of dying compared to when all three components were included. Women who left out all three components had almost three times the odds of dying from breast cancer or having distant metastatic disease compared to women who performed all three. The results were statistically significant and remained unchanged after adjustment for potential confounders, such as a family history of breast cancer.
Using prospectively collected data, the investigators conducted a case-control study of BSE involving patients in the Canadian National Breast Screening Study (CNBSS) to measure the effect of doing BSE on the risk of death due to breast cancer. The CNBSS is a multi-centre randomized controlled trial of screening for breast cancer that recruited 89,835 volunteers between 1980 and 1985; eligible women were aged 40 to 59 years, with no history of breast cancer, were not pregnant and had not undergone mammography in the 12 months before study entry.
All CNBSS participants completed self-administered questionnaires. At the first screen visit, clinical breast exams were performed and BSE instruction given. Each year, eligible participants returned for rescreening, which involved evaluation of BSE, a clinical breast exam, and further BSE instruction, with half the women also receiving annual mammography.
The researchers looked at the case histories of 220 women who either had died from breast cancer or had distant metastatic disease. Eligible subjects for the case-control study were all CNBSS participants except those diagnosed with breast cancer before their second year in the CNBSS, to eliminate the influence of pre-existing cancer. Ten randomly-selected controls were appropriately matched to each case.
To evaluate BSE performance the clinical examiner evaluated eight BSE components: (1) whether the participant included a visual examination; (2) how many fingers she used, did she use her thumb; (3) did she use the tips or pads of her fingers, did she use her entire hand; (4) was her search pattern concentric circles, spokes of a wheel pattern or random; (5) did she press down with a circular motion; (6) did she examine most or only part of her breasts; (7) did she examine her armpits; and (8) how often did she perform BSE.
"While we do need more evidence, this study shows that women who are doing BSE will only benefit from BSE if they do it well," says Dr. Cornelia Baines, an associate professor in the department of public health sciences and deputy director of the CNBSS, who was also involved in conducting the study. Harvey says he hopes this study motivates other researchers to collect more data to better determine if BSE is beneficial and, if it is, to document which components of BSE are important.
The study's investigators also included Anthony Miller, a professor emeritus in the department of public health sciences and director of the CNBSS, and Paul Corey, a professor in the department of public health sciences.
Harvey's research was supported by a Health Research Personnel Development Program doctoral fellowship from the Ontario Ministry of Health. Miller was supported in part by a National Health Scientist Award from Health Canada and Baines was supported in part by the National Cancer Institute of Canada.