Brief Summary: RATIONALE: Gathering information over time from blood samples and measurements of activity, sleep, mood, and cognition may help doctors learn more about fatigue in breast cancer survivors and plan the best treatment. PURPOSE: This clinical trial is studying fatigue in breast cancer survivors.

Detailed Description: OBJECTIVES: * To investigate the relationship between fatigue severity; protein biomarkers; and measures of activity, sleep, mood, and cognition in breast cancer survivors. * To identify and quantify serum biomarkers and underlying biological pathways unique to cancer-related fatigue syndrome in these survivors. * To map changes over time in order to explore the inter-relationships between these variables. OUTLINE: Participants undergo fatigue assessment by the Diagnostic Interview for Cancer Related Fatigue and the FACT-Fatigue questionnaire; psychological symptoms assessment by the Structured Clinical Interview for DSM-IV, Hospital Anxiety and Depression Scale, and the Insomnia Severity Index questionnaires; and quality of life assessment by the EORTC-QLQc30 and EORTC-QLQ-BR23 questionnaires twice approximately 3 months apart. Participants also undergo activity level, circadian rhythm, and sleep measurements by the Micro-mini® Motionlogger actigraphy and measurement of cognitive disturbances by the Cantabeclipse™ technology. Participants undergo blood sample collection for protein analysis by 2D gel electrophoresis and mass spectrometry.