Function-related indicators and outcomes of screening mammography in older women: evidence from the Breast Cancer Surveillance Consortium Cohort
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BACKGROUND: Previous reports suggested risk of death and breast cancer varied by comorbidity and age in older women undergoing mammography. However, impacts of functional limitations remain unclear. METHODS: We used data from 238,849 women in the Breast Cancer Surveillance Consortium-Medicare linked database (1999-2015) who had screening mammogram at ages 66-94 years. We estimated risk of breast cancer, breast cancer death, and non-breast cancer death by function-related indicator (FRI) which incorporated 16 claims-based items and was categorized as an ordinal variable (0, 1, and 2+). Fine and Gray proportional sub-distribution hazards models were applied with breast cancer and death treated as competing events. Risk estimates by FRI scores were adjusted by age and NCI comorbidity index separately and stratified by these factors. RESULTS: Overall, 9,252 women were diagnosed with breast cancer, 406 died of breast cancer, and 41,640 died from non-breast cancer causes. The 10-year age-adjusted invasive breast cancer risk slightly decreased with FRI score [FRI = 0: 4.0%, 95% confidence interval (CI) = 3.8-4.1; FRI = 1: 3.9%, 95% CI = 3.7-4.2; FRI ≥ 2: 3.5%, 95% CI = 3.1-3.9). Risk of non-breast cancer death increased with FRI score (FRI = 0: 18.8%, 95% CI = 18.5-19.1; FRI = 1: 24.4%, 95% CI = 23.9-25.0; FRI ≥ 2: 39.8%, 95% CI = 38.8-40.9]. Risk of breast cancer death was low with minimal differences across FRI scores. NCI comorbidity index-adjusted models and stratified analyses yielded similar patterns. CONCLUSIONS: Risk of non-breast cancer death substantially increases with FRI score, whereas risk of breast cancer death is low regardless of functional status. IMPACT: Older women with functional limitations should be informed that they may not benefit from screening mammography.
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