Objectives: To determine an upper age limit or quantifiable level of comorbidity that would render mammography screening ineffectual in decreasing mortality in women aged 65 and older.
Design: Retrospective cohort study.
Setting: Upper midwestern United States.
Participants: Five thousand one hundred eighty-six predominantly Caucasian women aged 65 to 101 diagnosed with invasive breast cancer from 1986 through 1994. Data were obtained from The Upper Midwest Tumor Registry System, a regional consortium database in Minnesota, North Dakota, and South Dakota.
Measurements: Relative risks (RRs) of death were computed for patients with mammographically detected tumors, stratified by age and comorbidity. Survival analysis was performed, stratified by level of comorbidity and method of tumor detection.
Results: Patients with mammographically detected tumors and no comorbidity experienced significantly lower RRs of death in every age group (range P <.001 to P =.039). Women with mammographically detected tumors and mild to moderate comorbidity had RRs of death as follows: age 65 to 69 (RR = 0.32, 95% confidence interval (CI) = 0.15-0.69), age 70 to 74, (RR = 0.45, 95% CI = 0.22-0.91); age 75 to 79 (RR = 0.47, 95% CI = 0.25-0.88), age 80 and older (RR = 0.52, 95% CI = 0.33-0.80). Women with severe or multiple comorbidities experienced no improvement in survival with mammographically detected tumors.
Conclusions: Mammographic detection of breast cancer may be associated with a significantly decreased risk of death for older women of all ages, even for women with mild to moderate levels of comorbidity, but for older women with severe or multiple comorbidities, mammography is not associated with improvement in overall survival.