Study to Evaluate the Feasibility of Twice Daily Use of Topical Azelaic Acid in Breast Cancer Patients Undergoing Radiation

Inclusion Criteria:

Age ≥ 18 years

• Self-reports as Black, Asian, Hispanic/Latin, ethnically originating from theMediterranean rim or Pacific rim, or she/he tans easily in the sun

• Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2 (Appendix 1,Section 18)

• Attestation by the patient that she/he is not pregnant, lactating, or planning tobecome pregnant, or planning to father a baby during the study period

• Histologic confirmation of breast malignancy (with TNM staging) If the patient didnot receive adjuvant chemotherapy, adjuvant radiation must start within 180 days oflumpectomy or mastectomy. If the patient received adjuvant chemotherapy, adjuvantradiation should start within 60 days of the last dose of chemotherapy

• Treatment plan includes one of the following:

• Conventionally fractionated whole breast radiation (45-50 Gray in 25 fractions)

• Moderately hypofractionated whole breast radiation (42.56 Gray in 16 fractionsor 40 Gray in 15 fractions)

• Conventionally fractionated chest wall radiation (45-50 Gray in 25 fractions)

• Partial breast radiation (42.56 Gray in 16 fractions, 40 Gray in 15 fractions,or 30 Gray in 5 fractions) if using 3D conformal radiation or if the tumor islocated close to the skin surface

• Treatment of the regional lymph nodes, a tumor bed boost (4-8 fractions), and use oftissue-equivalent bolus on the chest wall may be included at the discretion of thetreating physician.

• Radiation will be photon-based. Note: If the patient receives a boost, photonsand/or electrons may be used at the discretion of the treating physician.

Exclusion Criteria:

• Prior radiotherapy to any portion of the planned treatment site

• Current inflammatory breast cancer or gross dermal involvement at initiation ofradiotherapy

• Concomitant immunotherapy or cytotoxic chemotherapy. Concomitant HER2 directedtherapy or concomitant endocrine therapy is allowed

• Active rash or dermatitis within the treatment field, or a history of any rash ordermatologic condition within the treatment field

• Active collagen vascular diseases (ie lupus erythematosus, scleroderma,dermatomyositis)

• History of organ transplant or bone marrow transplant

• History of hypersensitivity or allergic reaction to any ingredients in the topicalazelaic acid formulation

• Has used within 28 days prior to baseline:

• topical retinoids to the breast

• oral retinoids

• systemic (oral or injectable) antibiotics known to have an impact on theseverity of skin rash or sun-sensitivity (eg, containing tetracycline and itsderivatives, erythromycin and its derivatives, sulfamethoxazole, ortrimethoprim)

• systemic corticosteroids or immunosuppressive drugs, except as part of standardchemotherapy treatment or used for an IV contrast allergy

• Has used on treated breast within 2 weeks prior to baseline:

• topical corticosteroids

• topical antibiotics

• topical medications for skin rash (eg, metronidazole, azelaic acid)

• Radiation therapy will be proton therapy or carbon therapy

• External beam partial breast irradiation, brachytherapy partial breast irradiation,or intraoperative radiation are included in the treatment plan Medical,psychological, or social condition that, in the opinion of the investigator, mayincrease the patient's risk or limit the patient's adherence with study requirements