Background: Women age 65 years and older account for most newly diagnosed breast cancers and deaths from breast cancer. Yet, older women are least likely to undergo mammography, perhaps because mammography's value is less well demonstrated in older women.
Objective: To investigate the relationship between prior mammography use, cancer stage at diagnosis, and breast cancer mortality among older women with breast cancer.
Design: Retrospective cohort study using the Linked Medicare-Tumor Registry Database.
Setting: Population-based data from three geographic areas included in the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program.
Participants: Women aged 67 and older diagnosed with a first primary breast cancer, from 1987 to 1993, residing in Connecticut, metropolitan Atlanta, Georgia, or Seattle-Puget Sound, Washington.
Measurements: Medicare claims were reviewed and women were classified according to their mammography use during the 2 years before diagnosis: nonusers (no prior mammograms), regular users (at least two mammograms at least 10 months apart), or peri-diagnosis users (only mammogram(s) within 3 months before diagnosis). Mammography utilization was linked with SEER data to determine stage at diagnosis and cause of death. Our main outcome variables were (1) stage at diagnosis, classified as early (in situ/Stage I) or late (Stage II or greater), and (2) breast cancer mortality, measured from diagnosis until death from breast cancer or end of the follow-up period (December 31, 1994).
Results: Older women who were nonusers of mammography were diagnosed with breast cancer at Stage II or greater more often than regular users (adjusted odds ratio (OR), 3.12; 95% confidence interval (CI), 2.74-3.58). This association was present within each age group studied. Nonusers of mammography were at significantly greater risk of dying from their breast cancer than regular users for all women (adjusted hazard ratio (HR), 3.38; 95% CI, 2.65-4.32) and for women within each age group. Even assuming a lead time of 1.25 years, nonusers of mammography continued to be at increased risk of dying from breast cancer. Our findings remained significant for all women and for the two youngest age groups (67-74 years, 75-85 years), although the benefit was no longer statistically significant for the oldest women (85 years and older).
Conclusions: Older women who undergo regular mammography are diagnosed with an earlier stage of disease and are less likely to die from their disease. These data support the use of regular mammography in older women and suggest that mammography can reduce breast cancer mortality in older women, even for women age 85 and older.