Summary: The Biostatistics Core (the designated Shared Research Resources Core) will provide expert guidance and support in the biostatistical aspects of the design, conduct and analysis of research projects generated under the Penn PROSPR Research Center grant. Core staff members will collaborate with project investigators at every stage: They have already assisted in the design of proposed projects, and they will continue to work with investigators in refining design and analysis plans. As studies proceed. Core staff members will monitor study databases, participate in the evaluation of data quality, and conduct any designated interim analyses. When studies are finished. Core staff will conduct correct and efficient data analyses, create graphs and tables, assist investigators with the preparation of presentations and manuscripts, and consult on the design of subsequent research. The Core staff members have extensive experience supporting research projects of all kinds in breast cancer and other forms of cancer. In particular, they have substantial expertise in comparative effectiveness research, cancer diagnostics, health economics, and the statistical evaluation of screening programs. Thus the Core is superbly qualified to provide biostatistical support of the highest quality to PCIPS.