Mammographic tissue, breast cancer risk, serial image analysis, and digital mammography. Part 2. Serial breast tissue change and related temporal influences.

The work presented herein is the second part of a review of breast tissue-related cancer-risk research. Briefly, in part 1, the tissue-risk research is discussed. In this part, factors that influence temporal breast tissue change are reviewed. Since breast composition is correlated with some of the known risk factors, understanding these influences may provide a mechanism for measuring the dynamics of breast cancer risk. The purpose of this work is to provide support for an automated serial mammography study under way at the authors' institution, where the digital mammographic images are acquired with a full-field digital mammography imaging system. At the initiation of the serial study, it was clear that the authors did not fully understand the nature of the problem: automatically comparing similar mammographic scenes acquired at different times. The evidence indicates that there are many factors that influence breast tissue at any given time and thus have the ability to alter the associated radiographic appearance over time. In general, the topics considered herein include aging; involution; breast development; exogenous and endogenous hormonal interactions such as hormone replacement therapy, oral contraceptive use, and menstrual timing; screening sensitivity issues and interval cancers; tumor growth rates; sojourn times; and lifestyle factors such as diet and exercise. Throughout this work, commentaries and suggestive strategies for automated serial image analysis are provided.