The goal of this study is to examine the role of Intraoperative Radiotherapy (IORT) in Ductal Carcinoma In-Situ (DCIS) and to improve the understanding of the clinical, radiographic, and patient-related impact of adopting IORT.

With advances in technology and screening, the overdiagnosis and overtreatment of ductal carcinoma in situ (DCIS) have increased. Minimizing treatment toxicity and cost is a high priority area of research. Intraoperative Radiation Therapy (IORT)is a form of radiation where a single high dose of irradiation is applied to the tumor bed at the time of lumpectomy. Its use has not been previously studied in DCIS. Proposed advantages include decreased toxicity to adjacent tissue and organs, reduction in healthcare costs, and improved quality of life. The investigators hypothesize that IORT is a safe and patient-friendly alternative to whole breast irradiation.

Inclusion Criteria:

• Pathologically confirmed DCIS of the breast
• Clinical ≤ 3.0 cm unifocal lesion
• No clinical or pathological evidence of nodal involvement
• Operable DCIS, suitable for breast conserving surgery
• Plans to administer irradiation to the breast only
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-3, however grade 4 patients may be enrolled at the discretion of the treating radiation oncologist
• Must have had a diagnostic mammogram or MRI performed within last 6 months
• Women of child-bearing potential must have a negative pregnancy test in accordance to institutional guidelines
• Women of child-bearing potential must agree to use adequate contraceptive precautions (defined as oral contraceptives, intrauterine devices, surgical contraceptives, or combination of condom and spermicide) from the time of negative pregnancy test through the radiation treatment period.
• English or Spanish speaking
• Able to sign informed consent
• Amenable to regular follow-up (according to research policies) for at least 5 years.

Exclusion Criteria:

• Histologic or clinical evidence of invasive breast cancer
• Multicentric cancer in the ipsilateral breast as diagnosed by clinical examination, imaging, or pathologic assessment, not amenable to excision with negative margins with a single lumpectomy
• Synchronous bilateral breast cancer at the time of diagnosis
• Pathologic or imaging evidence of lymph node involvement
• Any severe concomitant disease that may limit their life expectancy to less than 5 years.
• Prior history of breast cancer or in-field radiation in the ipsilateral breast.
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Pregnant or breast feeding women