Magnetic Resonance Imaging in Radiotherapy for Breast Cancer

Eligibility Criteria

• 1. Participants with an Eastern Cooperative Oncology Group (ECOG) performance status \<=2 (or Karnofsky ≥\>=60%, see Appendix A).
• 2. Participants with the ability to understand and the willingness to sign a written informed consent document.
• 3. Participants may separately enroll on therapeutic clinical trials when they enroll on this trial. Note: All interventions on this protocol are standard of care, so enrollment on other therapeutic protocols is allowed at the discretion of the treating physician.
• 4. Patients must have pathologically confirmed invasive or in situ breast cancer.
• 5. Patients must have tumors in which adjuvant breast radiotherapy following breast conserving surgery is indicated, as determined by the treating physician.
• 6. Patients must be female. Note: Male patients are excluded due to the rarity of male breast cancer and difficulty in pursuing breast conserving surgery for male patients.
• 1. Participants with a contraindication to MRI per the MRI checklist.
• 2. Patients with breast tumor or tumor bed not visualized at CT or MRI during RT planning.