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.