The first goal of this project is to validate the superiority of semi-permanent marks used in conjunction with specialized light-based surface imaging (SIGRT) in an effort to phase out the use of permanent tattoos for the investigator's patients. The secondary goal of this project is to validate the superiority of specialized light-based surface imaging for daily radiation set-up compared to standard-of-care imaging methods using ionizing radiation, such as weekly port films or cone-beam CT (CBCT) scans during a radiation therapy course for breast cancer.

This study uses surface imaging for breast patients to standardize or normalize planning position & minimize variability of port films thus reducing systematic error. The primary objective of this study is to demonstrate the superiority of using surface imaging to combine an ideally gated treatment planning CT and verification images timed to the breathing cycle, quantified as the total within-subject variation of the measured location relative to current methods of radiation delivery not using this approach. The secondary objective is to demonstrate the superiority of specialized light-based surface imaging for daily radiation set-up without tattoos compared to standard-of-care methods with regard to the total within-subject variation of the measured location determined by weekly port films during a course of radiation for breast cancer.

Inclusion Criteria:

• 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 in Exclusion Criteria

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