Screening mammography and late-stage breast cancer: a population-based study

Among 50- to 69-year-old women, randomized clinical trials show breast cancer mortality reductions from screening mammography. However, few studies examine the long-term health effects and outcomes from screening mammography in community practice. The purpose of this study was to evaluate one approach for determining the effectiveness of screening mammography, as it is practiced in community settings, and to measure the prevalence of prior screening mammography among women with incident breast cancer.

This study was a population-based survey of the general community. Participants were 406 women with breast cancer diagnosed in 1993. The main outcome measure was breast cancer, late stage at diagnosis or fatal within 2 to 3 years of diagnosis.

Sixty-four (57.7%) of 111 women with late-stage and 123 (42.1%) of 292 women with early-stage breast cancer did not have a screening mammogram in the 4 calendar years (1989-1992) before diagnosis. Relative to women with early-stage breast cancer, mammography nonuse in 1989-1992 was significantly more frequent among women with late-stage breast cancer (age-adjusted odds ratio 2.3, 95% confidence interval 1.3-4.3). Prior mammography was particularly infrequent among 42 women with breast cancer incident in 1993 and fatal before January 1996.

Prior mammography among women with late-stage or fatal breast cancer was relatively infrequent. Late-stage or fatal breast cancer lacking prior mammography constitutes a missed public health opportunity. Also, this population-based study showed the expected association between prior mammography and late-stage or fatal breast cancer. These results are consistent with the effective practice of mammography in a community setting. The results illustrate and validate a public health approach that uses prior mammography histories among women with incident breast cancer to evaluate mammography penetration and quality in defined communities.