Breast Fractionation Study - Standard Versus Investigational Fractionation Trial - Nodal Radiation

Inclusion Criteria: * Age 18 years and older * ECOG performance status 0-2 * Ability to understand and willingness to sign a written informed consent document * Stage pT1-3, pN0-3, M0 histologically proven breast cancer no matter the status of ER/PR/HER2 receptor testing * Managed with either mastectomy or breast conserving surgery * Suitable for radiation therapy to the breast/chest wall and regional lymph nodes * Neoadjuvant and adjuvant systemic therapy with chemotherapy, endocrine therapy and anti-HER2 therapy is accepted * Neoadjuvant radiotherapy (reverse sequencing) accepted * Breast implants and expanders are accepted * Patients with connective tissue disease are allowed if the treating radiation oncologist finds radiation therapy indicated * Life expectancy minimum 10 years * Patients with non-breast malignancies are accepted if the patient has been disease free for five years and/or has a low risk of recurrence as estimated by the treating radiation oncologist (to be determined at initial patient appointment) Exclusion Criteria: * Prior radiotherapy to the ipsilateral breast or chest wall * Pregnancy or lactation * Radiosensitivity syndrome * Permanent pacemaker/defibrillator within radiotherapy field * Oncoplastic surgery where boost volume unacceptable (clinician discretion) * Conditions indicating that the patient cannot go through radiation therapy or follow up, or a condition where the treating oncologist thinks the patient should not participate in the trial (for example, language barriers)