Prospective estimation of rates of change in mammographic parenchymal patterns: influence of age and of hormone replacement (HRT) therapy

The objective of the study described in this presentation was to assess the effect of age, breast size and use of HRT on the rate of change of mammographic parenchymal patterns, and the effect of age on the probability of misclassification between patterns. It was designed as a longitudinal study of the members of the treatment arm of a nonrandomized screening trial. A model was fitted to the data comprising the observed Wolfe patterns on each woman, with age and breast size as predictors of breast density at first screen, age and HRT use as predictors of change in density at future screens, and age as a predictor of misclassification of true density between favourable (nondense) and unfavourable (dense) patterns (according to the Wolfe classification). The probability of being in a nondense, favourable state increases with age, as does the rate of change from dense to nondense patterns. These results are consistent with previous work. The probability of nondense patterns and the rate of change to nondense patterns are reduced with HRT use. Errors of classification are relatively rare, but are dependent on the age of the subject.