Effect of breast self-examination techniques on the risk of death from breast cancer.

OBJECTIVE To measure the effect of breast self-examination (BSE) technique and frequency on the risk of death from breast cancer. DESIGN Case-control study nested within the Canadian National Breast Screening Study (NBSS). SETTING The Canadian NBSS, a multicentre randomized controlled trial of screening for breast cancer in Canadian women. SUBJECTS The case subjects were 163 women who had died from breast cancer and 57 women with distant metastases. Ten control subjects matched by 5-year age group, screening centre, year of enrolment and random allocation group were randomly selected for each case subject. EXPOSURE MEASURES Self-reported BSE frequency before enrolment in the NBSS, annual self-reports of BSE frequency during the program and annual objective assessments of BSE technique. OUTCOME MEASURES Odds ratios (ORs) associated with BSE practice were estimated by conditional multiple logistic regression modelling, which permitted control of covariates. RESULTS Relative to women who, when assessed 2 years before diagnosis, examined their breasts visually, used their finger pads for palpation and examined with their 3 middle fingers, the OR for death from breast cancer or distant metastatic disease for women who omitted 1, 2 or 3 of these components was 2.20 (95% confidence interval [CI] 1.30 to 3.71, p = 0.003). The OR for women who omitted 1 of the 3 components was 1.82 (95% CI 1.00 to 3.29, p = 0.05), for those who omitted 2 of the 3 components, 2.84 (95% CI 1.44 to 5.59, p = 0.003), and for those who omitted all 3 components, 2.95 (95% CI 1.19 to 7.30, p = 0.02). The results remained unchanged after adjustment for potential confounders. CONCLUSION The results, obtained with the use of prospectively collected data, suggest that the performance of specific BSE components may reduce the risk of death from breast cancer.