A Study of Different Skin Care Approaches to Prevent Skin Reactions in People With Breast Cancer Receiving Radiation Therapy After Mastectomy

Inclusion Criteria: * Patients must have pathologically confirmed breast cancer. * Patients will have an assigned sex of female at birth. * Patients will have undergone mastectomy without breast reconstruction surgery or with immediate reconstruction using one or more of an expander, implant, or flap-based approach. * Patients will have pathologic stage T1-3 N0-1 M0 disease with indication for comprehensive post-mastectomy radiotherapy to the ipsilateral chest wall and regional lymph node basins (axilla, SCV, IMN). * Patient/LAR willing to sign and date consent form * Age ≥ 18 * ECOG Performance Status of ≤ 2 Exclusion Criteria: * Patients with indication for escalated skin dose (dermal invasion, skin involvement, positive surgical margin). * Patients planned to receive a scar or chest wall, or other boost. * Patients planned to receive post-mastectomy radiotherapy using a hypofractionated regimen (ie., \>2.0 Gy per fraction). * Patients who have a diagnosis of connective tissue disorder or collagen vascular disorder. * Patients who have an active rash in the cervical or thoracic region. * Patients taking systemic steroids \>10 mg/day. * Patients on active antimicrobial treatment at the time of study enrollment. * Patients with a prior history of organ or bone marrow transplant. * Patients who are pregnant or nursing * Prior Treatment: * Patients with prior history of radiotherapy to the neck, thorax or abdomen. * Resolution of all toxicities of prior therapy or surgical procedures to baseline or Grade 1 (except for hypothyroidism requiring medication, which must have resolved to Grade ≤2, alopecia, and other toxicities considered clinically nonsignificant and/or stable on supportive therapy as determined by the investigator). * Comorbid conditions: o Active infection requiring parenteral antibiotic(s) * Concomitant Medications: o Concurrent systemic therapy during the course are not allowed, including cytotoxic chemotherapy, immunotherapy, and targeted therapy. Last dose of these agents must be delivered at least 2 weeks prior to start of radiotherapy and not to be restarted until at least 2 weeks following completion of radiotherapy. Endocrine therapy, pembrolizumab, Herceptin, Perjeta, and Kadcyla are allowed. Concurrent oral steroid medications are not allowed. * Allergies: * History of allergic reaction to the study agent(s), compounds of similar chemical or biologic composition to the study agent (s) (or any of its excipients).