Mammography is the most effective method for breast cancer screening available today. However,
the low positive predictive value of breast biopsy resulting from mammogram interpretation leads
to approximately 70% unnecessary biopsies with benign outcomes. To reduce the high number of
unnecessary breast biopsies, several computer-aided diagnosis CAD systems have been proposed
in the last several years. These systems help physicians in their decision to perform a breast biopsy
on a suspicious lesion seen in a mammogram or to perform a short term follow-up examination
instead. We present two novel CAD approaches that both emphasize an intelligible decision process
to predict breast biopsy outcomes from BI-RADS™ findings. An intelligible reasoning process is an
important requirement for the acceptance of CAD systems by physicians. The first approach induces a global model based on decison-tree learning. The second approach is based on case-based
reasoning and applies an entropic similarity measure. We have evaluated the performance of both
CAD approaches on two large publicly available mammography reference databases using receiver
operating characteristic ROC analysis, bootstrap sampling, and the ANOVA statistical significance
test. Both approaches outperform the diagnosis decisions of the physicians. Hence, both systems
have the potential to reduce the number of unnecessary breast biopsies in clinical practice. A
comparison of the performance of the proposed decision tree and CBR approaches with a state of
the art approach based on artificial neural networks ANN shows that the CBR approach performs
slightly better than the ANN approach, which in turn results in slightly better performance than the
decision-tree approach. The differences are statistically significant p value 0.001. On 2100
masses extracted from the DDSM database, the CRB approach for example resulted in an area
under the ROC curve of Az=0.89±0.01, the decision-tree approach in Az=0.87±0.01, and the
ANN approach in Az=0.88±0.01