Cumulative Incidence of Non-breast Cancer Mortality and Breast Cancer Risk by Comorbidity and Age among Older Women Undergoing Screening Mammography: The Medicare-linked Breast Cancer Surveillance Consortium Cohort Study

Due to an increasing comorbidity burden with aging, the margin of benefit from screening mammography in women ages ≥65 is highly variable. This study examined 10-year cumulative risk of non-breast cancer mortality and breast cancer by comorbidity and age in a screening population. Methods: We used prospective cohort data from the Breast Cancer Surveillance Consortium (BCSC), which included 198,362 women ages ≥65 years who have undergone at least one screening mammogram. We calculated cumulative incidence of non-breast cancer mortality and risk of breast cancer 10 years following the screening mammogram for women ages 65–74, 75–84 and ≥85 years stratified by the Charlson Comorbidity Index (CCI scores 0, 1 and ≥2). Results: During a median follow-up time of 8.1 years (interquartile range, 4.6 to 10 years), 34,768 died from non-breast cancer causes and 6,327 women were diagnosed with invasive breast cancer of whom 359 died from breast cancer and 942 from non-breast cancer causes. The 10-year cumulative risk of invasive breast cancer following a screening mammogram did not significantly decrease with elevating CCI score and age for women ages 65–74 [CCI 0 = 4.0% (95% CI, 3.9%–4.1%) vs. CCI ≥2 = 3.8% (95% CI, 3.3%–4.3%)], ages 75–84 [CCI 0 = 3.7% (95% CI, 3.5%–3.9%) vs. CCI ≥ 2 = 3.4% (95% CI, 2.8%–4.0%)], and ages ≥85 [CCI 0 = 2.7%, (95% CI, 2.3%–3.2%) vs. CCI ≥ 2 = 2.5% (95% CI, 1.4%–3.6%)]. Cumulative risk of non-breast cancer mortality significantly increased with increasing CCI and age for women ages 65–74 [CCI 0 = 11% (95% CI, 10%–11%] vs. CCI ≥ 2 = 45% (95% CI, [43%–46%)], ages 75–84 [CCI 0 = 29% (95% CI, 29%–30%) vs. CCI ≥2 = 62% (95% CI, 60%–63%)], and ages ≥85 [CCI 0 = 59%, (95% CI, 57%–60%) vs. CCI ≥2 = 84% (95% CI, 81%–86%)]. Conclusion: Risk of non-breast cancer mortality was high and significantly increased with rising comorbidity burden and age whereas breast cancer risk was low and non-significantly decreased with both. These results suggest that women with a CCI score of ≥2 or ages ≥75 years may experience minimal benefit from continuing routine screening mammography. Future research is needed to delineate the specific benefits and harms of screening mammography in subsets of older women defined by age and comorbidity burden.