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).