Many patients receiving radiation therapy for breast cancer experience fatigue although doctors do not fully understand why. The purpose of this study is to test if patients who experience fatigue during radiation treatment for breast cancer have changes in their capability to perform exercise on a treadmill.

Inclusion Criteria:

• Female
• ECOG performance status 0 or 1
• Medical clearance from attending radiation oncologist or medical oncologist to undergo a symptom-limited CPET
• Currently undergoing intact breast radiotherapy for early stage breast cancer (including TisN0, T1N0, T2N0) or has completed intact breast RT in the last 3 months.
• Receiving or received a prescribed dose of 4240 cGy in 16 fractions to the whole breast without treatment directed at nodal basins. Patients may also be receiving or have received a boost to the lumpectomy bed at the discretion of the treating physician.
• Subjects may be treated in the supine or prone position at the discretion of the treating physician.
• Subjects may be treated with or without a deep inspiratory breath hold technique at the discretion of the treating physician.
• Identified by the treating radiation oncologist as having significant treatment-related fatigue or minimal treatment-related fatigue and not simply baseline fatigue. A score of "0" on the RTOG fatigue scale will be considered minimal fatigue, while a score of "2" or greater will be considered significant fatigue (moderate fatigue causing difficulty performing some ADLs).

Exclusion Criteria:

• Currently undergoing post-mastectomy radiation

• Has received chemotherapy previously or has a plan to receive chemotherapy during the timeframe of study assessment.

• Any of the following absolute contraindications to CPET, as per American Thoracic Society (ATS) recommendations

  • Acute myocardial infarction (within 3-5 days of any planned study procedures)
  • Unstable angina
  • Uncontrolled arrhythmia causing symptoms or hemodynamic compromise
  • Recurrent syncope
  • Active endocarditis
  • Acute myocarditis or pericarditis
  • Symptomatic severe aortic stenosis
  • Uncontrolled heart failure
  • Acute pulmonary embolus or pulmonary infarction within 3 months of any planned study procedures
  • Thrombosis of lower extremities
  • Suspected dissecting aneurysm
  • Uncontrolled asthma
  • Pulmonary edema
  • Room air desaturation at rest ≤ 85%
  • Respiratory failure
  • Acute non-cardiopulmonary disorders that may affect exercise performance or be aggravated by exercise (i.e. infection, renal failure, thyrotoxicosis)
  • Mental impairment leading to inability to cooperate

Patients who are undergoing or have recently completed radiotherapy for breast cancer (in the last 3 months) will be assessed in outpatient clinics of the Radiation Oncology Department of MSKCC. The protocol is available for consenting only at OneMSK Sites Basking Ridge, Rockville Center, Commack, Monmouth and Westchester.