Inclusion Criteria:

• Arm B: Breast cancer arm
• 1. Women with breast cancer, treated with ipsilateral i) Simple (total) mastectomy (nipple sparing mastectomy is same as total mastectomy), OR ii) Modified radical mastectomy, OR iii)Radical mastectomy
• 2. Histological diagnosis of invasive ductal or lobular carcinoma (diagnosed within 2 years of enrollment)
• 3. Planned to receive adjuvant chest wall radiation of at least 40Gy or higher biologically equivalent dose (BED)
• 4. Age 18 years or older
• 5. Eastern Cooperative Oncology Group (ECOG) performance status 0 to 2
• 6. Written Informed Consent
• 7. History and Physical within 12 weeks of enrollment
• Arm A: Head \& Neck cancer arm
• 1. Patients with squamous cell carcinoma of the head and neck confirmed with institutional pathology (diagnosed within 2 years of enrollment)
• 2. Planned to receive concurrent chemoradiation with any radiosensitizing regimen (such as cisplatin) of at least 60 Gy or higher (note: chemotherapy per medical oncology and otolaryngology).
• 3. Age 18 years or older
• 4. ECOG performance status 0 to 2
• 5. Written Informed Consent
• 6. History and Physical within 12 weeks of enrollment

Exclusion Criteria:

• Arm B: Breast Cancer arm
• 1. Prior chest wall radiotherapy
• 2. Any serious medical condition or illness that would preclude the safe administration of the study drug including, but not limited to: active infection, symptomatic heart failure, unstable angina, psychiatric illness or social situations that would limit compliance with treatment
• 3. Concurrent chemotherapy
• 4. Biopsy-proven epidermal involvement or positive margins
• 5. Open wound at time of consultation, or delayed surgical wound healing as defined as open wound \>8 weeks post-op
• 6. Known active collagen vascular disease such as systemic lupus erythematous, scleroderma or dermatomyositis.
• 7. Allergy or sensitivity to proton pump inhibitors
• 8. Pregnancy or breast feeding
• 9. Use of clopidrogrel, St. Johns Wort, rifampin, or methotrexate
• Arm A: Head \& Neck cancer arm
• 1. Prior head and neck radiotherapy
• 2. Any serious medical condition or illness that would preclude the safe administration of the study drug including, but not limited to, active infection, symptomatic heart failure, unstable angina, psychiatric illness or social situations that would limit compliance with treatment
• 3. Lack of concurrent chemotherapy
• 4. Open wound at time of simulation
• 5. Known active collagen vascular diseases such as systemic lupus erythematous, scleroderma or dermatomyositis.
• 6. Allergy or sensitivity to proton pump inhibitors
• 7. Pregnancy or breast feeding (pregnancy test prior to CT simulation if the patient is not on a medication that prevents pregnancy)
• 8. Use of clopidrogrel, St. Johns Wort, rifampin, or methotrexate