Risk of subsequent breast cancer in relation to characteristics of screening mammograms from women less than 50 years of age.

This investigation was conducted to assess the predictive value of calcifications and densities in mammograms from women <50 years of age for subsequent diagnosis of breast cancer. In a population-based study, prior screening mammograms taken before age 50 in 547 women with breast cancer and 472 controls were reviewed by a single radiologist. The relative risk (RR) of subsequent breast cancer increased with the percentage of the area of the mammogram that was mammographically dense [RR in succeeding quartiles of density = 1.0, 1.7 (1.1-2.6), 3.3 (2.2-5.0), and 4.0 (2.7-6.0)]; in relation to Wolfe parenchymal pattern class P2 [RR = 3.1 (2.2-4.3)] or DY [RR = 5.6 (3.2-10.0)]; and in relation to calcifications of class 1 (pleomorphic of any distribution) or class 2 (various morphological types that are regional, grouped, clustered, segmental, or linear in distribution) [RR = 3.0 (1.4-7.1), and 1.8 (1.2-2.6), respectively]. Women with radiographically dense mammograms and class 1 or 2 calcifications were at >10- and approximately 6-fold greater risk, respectively, than women with breasts of low density and no calcifications. Densities and parenchymal patterns were most strongly associated with breast cancer being diagnosed in the next 3 years. Class 1 and 2 calcifications were most strongly predictive of an increased risk in 3-6 years. Class 1 calcifications were strongly predictive of the breast in which the subsequent cancer occurred. Women <50 years of age with class 1 or 2 calcifications or mammographically dense breasts, or both, should receive high priority for further evaluation and regular breast cancer screening.