Accuracy of screening mammography in older women.
The objective of our study was to determine the accuracy and cancer detection rate of screening mammography in women as they age. Using data from the Vermont Breast Cancer Surveillance System (1996-2006), we calculated the sensitivity, specificity, positive predictive value, negative predictive value, and cancer detection rate by decade of age for 403,448 mammograms of 96,193 women 50-101 years old. Confounding variables were assessed using logistic regression analysis. The sensitivity of screening mammography increased from 77.3% for the 50- to 59-year-old group to 93.8% for the 90- to 101-year-old group (p = 0.015). Specificity increased from 98.7% to 98.8% at age 50-59 compared with age 90-101 (p < 0.001), respectively. The cancer detection rate increased from 3.7 cases per 1000 mammograms at age 50-59 to 14.4 cases per 1000 mammograms at age 90-101 (p < 0.001). The prevalence of breast cancer increased from 4.8% to 15.4% across age groups (p < 0.001) as did the positive predictive value from 22.2% to 55.6% (p <0.001). There was no evidence of confounding by body mass index, breast density, or other factors. Tumors were more likely to be small, hormone receptor-positive, and more invasive as women aged. Accuracy parameters were all associated with age without evidence of confounding by regression analysis. Screening mammography is more accurate in older women than in younger women, suggesting that it may be of value in assessing women in all age groups. These data do not address the impact of mammography screening on mortality or breast cancer outcomes.