Inclusion Criteria:
- Female
- New diagnosis of Ductal Carcinoma in Situ (DCIS) and/or invasive breast carcinoma per histologic evaluation
- Age 40-85 at diagnosis
- Previous lumpectomy with surgical margins histologically free of invasive tumor and DCIS as determined by the pathologist
- T stage of Tis, T1, or T2
- T2 tumors must be ≤3 cm in maximum diameter
- If the tumor is human epidermal growth factor receptor (HER2)-positive, the patient is planning to receive or has already received HER2-directed therapy
- For patients with invasive breast cancer, an axillary staging procedure must be performed (either sentinel node biopsy alone or axillary dissection [with a minimum of 6 axillary nodes removed]) and the axillary node(s) must be pathologically negative Note: N0(i+) is not an exclusion criterion
Note: Patients meeting all of the following criteria are not required to undergo the axillary staging procedure:
- ≥70 years of age
- Estrogen receptor (ER)+, progesterone receptor (PR)+/-, HER2-
- Grade 1-2 breast cancer
- Tumor ≤2 cm in size
Note: If patients meet all the following criteria, the decision to avoid sentinel lymph node biopsy can be at the discretion of the breast surgeon:
- 50-69 years of age
- Grade 1-2 breast cancer
- Clinically negative axilla by ultrasound and/or magnetic resonance imaging (MRI)
- ER+, PR+, HER2-
- Tumor ≤2 cm in size
- Agrees to comply with aromatase inhibitor recommendation
- Ability to begin brachytherapy within 12 weeks following lumpectomy, re- excision of margins, or completion of chemotherapy
- Ability to understand and the willingness to sign a written informed consent document
Exclusion Criteria:
- Pregnant or breastfeeding
- Active collagen-vascular disease
- Paget's disease of the breast
- Any prior history of DCIS or invasive breast cancer prior to the current diagnosis
- Any prior history of breast radiation therapy (RT) or thoracic RT for any condition
- Multicentric carcinoma (DCIS or invasive)
- Synchronous bilateral invasive or non-invasive breast cancer
- Surgical margins that cannot be microscopically assessed or that are positive
- Treatment with neoadjuvant chemotherapy
- Excision cavity that cannot be clearly delineated or is not amenable to implant per the treating investigator
- Medical, psychological, or social condition that, in the opinion of the investigator, may increase the patient's risk or limit the patient's adherence with study requirements