This study will investigate a novel approach to marking surgical cavity margins following tumor resection, to allow for more accurate radiotherapy following oncoplastic surgery. Our proposed cavity marking schema will allow radiation oncology to identify the cavity margins more accurately on CT simulation for radiation planning and delivery. This cavity marking schema also provides more accurate margin identification in patients recommended for re-excision of close or positive margins.

Inclusion Criteria:

• Adults ≥ 18 years of age.
• A pathological diagnosis consistent with non-invasive ductal carcinoma in-situ (DCIS) and invasive breast cancer, Tis-T3N0-3M0
• Subject is planning to undergo or has undergone breast conservation surgery and oncoplastic reconstruction with cavity marking surgery.
• ECOG Performance status of 0-1
• Written informed consent obtained from the subject and the subject agrees to comply with all the study-related procedures.
• Subjects must not have more than one active malignancy at the time of enrollment (Subjects with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen [as determined by the treating physician or approved by the PI] may be included).
• Subjects of childbearing potential (SOCBP) must be using an adequate method of contraception to avoid pregnancy during surgery and radiation therapy. Prior to study enrollment, subjects of childbearing potential must be advised of the importance of avoiding pregnancy during the surgery and radiation portions of the trial and the potential risk factors for an unintentional pregnancy. SOCBP includes any subject who has experienced menarche and who has not undergone successful surgical sterilization (hysterectomy, bilateral tubal ligation, or bilateral oophorectomy) or who is not post-menopausal. Post-menopause is defined as amenorrhea that has lasted for ≥ 12 consecutive months without another cause.

Exclusion Criteria:

• Patient not recommended for, or have declined, adjuvant radiotherapy
• Subjects with prior ipsilateral breast surgery and identifiable surgical clips.
• Subjects who are confirmed to be pregnant or breastfeeding.
• History of any other disease, metabolic dysfunction, clinical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of protocol therapy or that might affect the interpretation of the results of the study or that puts the subject at high risk for treatment complications, in the opinion of the treating physician.
• Prisoners or subjects who are involuntarily incarcerated, or subjects who are compulsorily detailed for treatment of either a psychiatric or physical illness.