• Age ≥ 18 years
• Biologically female
• Ability to provide informed written consent in either English or Spanish
• Surgical pathology and staging scans must demonstrate Ductal carcinoma in situ (DCIS) or invasive breast cancer, Stages 0, 1, 2, and 3
• Patient will undergo adjuvant radiation therapy as a part of multimodality breast cancer treatment with plans for tangent field radiation treatment with or without loco-regional lymph node targeting, based on the clinical judgement of the treating physician
• Willingness to maintain temporary skin markings for a part of their of radiation therapy duration
• Absence of any conditions that may affect ability to have either tattoos or skin markings, as discussed

Exclusion Criteria:

• Age < 18 years
• Biologically non-female
• Inability or unwillingness of subject to give written informed consent
• Patients found at presentation to have very locally-advanced cancer (e.g. inflammatory breast cancer) or metastatic breast cancer (Stage 4)
• Patients that will be treated with a deep-inspiration breath hold technique (typically younger patients being treated for left-sided tumors)
• Current pregnancy, as this is a contraindication to receiving radiation therapy
• History of prior radiotherapy to the chest wall or torso
• Known allergy / sensitivity to standard medical marking tattoo ink (by design non-toxic, low-allergy), skin marking paint, or medical tape (e.g. Tegaderm)
• Active drug or alcohol use or dependence evidenced by patient record and/or self-report that, in the opinion of the investigator, would interfere with adherence to daily radiation therapy