Using an observational prospective design, potential subjects will be identified and screened for eligibility via medical record review of breast cancer patients scheduled for radiation therapy at Duke Radiation Oncology Clinic. Subjects who agree to participate will be asked to complete study questionaires prior to the start of radiation therapy and again during the last week of therapy.

Exercise behavior will be defined as patient reported mean total minutes (frequency x duration) of mild, moderate, and vigorous-intensity physical exercise per week over the past month at baseline (prior to enrollment in the study). In addition we will collect patient reported mean total minutes per week of mild, moderate, and vigorous-intensity physical exercise over the course of radiation therapy.Baseline characteristics including demographic data (age, education, employment) as well as BMI, waist to hip ratio, and health comorbidities (including smoking status, cardiovascular disease, and diabetes) will also be collected. BMI and health comorbidities will be extracted from the chart. Patient-Reported Outcomes will include QOL, fatigue, depression, pain and sleep. QOL will be assessed using the Functional Assessment of Cancer Therapy (FACT) scale developed for the assessment of patient symptoms and QOL in cancer patients. Fatigue will be assessed using the 13-item FACT-fatigue scale for the assessment of fatigue in cancer patients.Skin toxicity will be defined as radiation dermatitis, pruritus, and pain.

Lymphedema will be assessed by measuring limb girth. Measurements will be taken by first marking both limbs while patient is lying supine, starting at the ulnar styloid at 5cm intervals on the length of the arms. The diameter of the limb will then be measured at these markings. Based on these measurements, the affected limb will be compared to the unaffected limb. Range of motion will be defined as reduced abduction compared to the contralateral shoulder . All measurements will be taken with a goniometer.

Inclusion Criteria:

• Women with a biopsy-proven diagnosis of ductal carcinoma in situ or invasive breast carcinoma
• Definitive radiation treatment planned to the chest and/or regional nodes
• 18 years of age or older
• Signed study-specific informed consent

Exclusion Criteria:

• Significant mental disorders making informed consent difficult or mental impairment leading to inability to cooperate
• Karnofsky Performance Status (KPS) < 70%

Subjects with biopsy proven ductal carcinoma in situ or invasive breast carcinoma scheduled to receive definitive treatment in the Department of Radiation Oncology at Duke will be potentially eligible for this study.