MAMMOGRAPHY USE HELPS TO EXPLAIN DIFFERENCES IN BREAST-CANCER STAGE AT DIAGNOSIS BETWEEN OLDER BLACK-AND-WHITE WOMEN

Background: Older black women are less likely to undergo mammography a nd are more often given a diagnosis of advanced-stage breast cancer th an older white women. Objective: To investigate the extent to which pr evious mammography explains observed differences in cancer stage at di agnosis between older black and white women with breast cancer. Design : Retrospective cohort study using the Linked Medicare-Tumor Registry Database. Setting: Population-based data from three geographic areas o f the United States included in the National Cancer Institute's Survei llance, Epidemiology, and End Results (SEER) program (Connecticut; met ropolitan Atlanta, Georgia; and Seattle-Puget Sound, Washington). Part icipants: Black and white women 67 years of age and older in whom brea st cancer was diagnosed between 1987 and 1989. Measurements: Medicare claims were used to classify women according to mammography use in the 2 years before diagnosis as nonusers (no previous mammography), regul ar users (greater than or equal to 2 mammographies done at least 10 mo nths apart), or peri-diagnosis users (mammography done only within 3 m onths before diagnosis). Information on mammography use was linked wit h SEER data to determine cancer stage at diagnosis. Stage was classifi ed as early (in situ or local) or late (regional or distant). Results: Black women were more likely to not undergo mammography (odds ratio [ OR], 3.00 [95% Cl, 2.41 to 3.75]) and to be given a diagnosis of late- stage disease (OR, 2.49 [CI, 1.59 to 3.92]) than white women. When wom en were stratified by previous mammography use, the black-white differ ence in cancer stage occurred only among nonusers (adjusted OR, 2.54 [ CI, 1.37 to 4.71]). Among regular users, cancer was diagnosed in black and white women at similar stages (adjusted OR, 1.34 [CI, 0.40 to 4.5 1]). In logistic modeling, previous mammography alone explained about 30% of the excess late-stage disease in black women. In a separate mod el, previous mammography explained 12% of the excess late-stage diseas e among black women after adjustment for sociodemographic and comorbid ity information. Conclusion: Differences in breast cancer stage at dia gnosis between older black and white women are related to previous mam mography use. Increased regular use of mammography may result in a shi ft toward earlier-stage disease at diagnosis and narrow the observed d ifferences in stage at diagnosis between older black and white women.