Breast cancer mortality in relation to receipt of screening mammography: a case-control study in Saskatchewan, Canada.

Abstract

The efficacy of screening mammography in reducing breast cancer mortality continues to be controversial. In addition, few data exist on the efficacy of screening mammography in women 70years of age or older. An organized screening mammogram program has existed in Saskatchewan since the mid-1990s. It offers mammography every 2years to women ≥50years of age. We conducted a population-based case-control study to evaluate the efficacy of screening mammography, as practiced in Saskatchewan, Canada. Cases (n=501) were women who died of breast cancer during 1995-2008 and were at least 52years of age at the time of their diagnosis. Controls (n=5,009) were matched to cases on birth year and duration of healthcare coverage prior to the cases' breast cancer diagnosis date. In cases and controls, receipt of screening mammography during the several years up to and including the date of the case's diagnosis of breast cancer was ascertained from the records of the screening program. Receipt of a screening mammogram in the preceding 2years was more common among controls (53%) than cases (37%), OR 0.51 (95% CI 0.42-0.62). A decreased risk was observed among women in all age groups, including those 70-79years (OR 0.40; 95% CI 0.27-0.60). Our findings suggest that receipt of screening mammography among women in Saskatchewan has been associated with a decreased risk of death from breast cancer.