This phase II trial studies how well accelerated partial breast irradiation (APBI) using high-dose rate (HDR) brachytherapy works in treating patients with breast cancer that has not spread beyond the breast or the axillary lymph nodes (early-stage) after surgery. Radiation therapy uses a type of energy to kill cancer cells and shrink tumors. Brachytherapy is a type of internal radiation therapy that provides radiation inside the breast to any remaining tumor cells next to the space where the tumor was removed, and is given over a shorter amount of time than standard radiation therapy. Giving accelerated partial breast irradiation (APBI) using high-dose rate (HDR) brachytherapy may reduce the overall time that radiation is delivered to the tumor cells.

PRIMARY OBJECTIVES:

I. To determine the toxicity rate with shorter courses of accelerated partial breast irradiation (APBI) delivered with a breast brachytherapy applicator.

SECONDARY OBJECTIVES:

I. To determine the 3-year actuarial local control rate with abbreviated accelerated partial breast irradiation (APBI).

II. To assess the rate of excellent or good cosmesis at 2-years after shorter courses of APBI and to identify co-variants associated with and predictive of poor cosmetic outcome in women treated with an overnight treatment course of APBI.

OUTLINE:

Within 1-5 days after balloon placement, patients undergo accelerated partial breast irradiation (APBI) using high-dose rate (HDR) brachytherapy over 15-60 minutes for 2-3 days.

After completion of study treatment, patients are followed up at 2-8 weeks and then at least annually for 2 years.

Inclusion Criteria:

• Must sign informed consent
• Surgical treatment of the breast must have been lumpectomy; the margins of the resected specimen must be histologically free of tumor (negative surgical margins per National Surgical Adjuvant Breast and Bowel Project [NSABP] criteria)
• On histologic examination, the tumor must be ductal carcinoma in situ (DCIS) and/or invasive breast carcinoma
• For patients with invasive breast cancer, an axillary staging procedure must be performed (either sentinel node biopsy [SNB] alone or axillary dissection [with a minimum of six axillary nodes removed], and the axillary node[s] must be pathologically negative); patients over 70 with estrogen receptor positive (ER+) tumors no greater than 2 cm do not require axillary evaluation, but MUST be clinically node negative on examination and all available imaging (clinical N0)
• The T stage must be Tis, T1, or T2; if T2, the tumor must be =< 3.0 cm in maximum diameter
• Estrogen receptor positive tumor and/or progesterone receptor positive tumor

Exclusion Criteria:

• Pregnant or breast-feeding
• Active collagen-vascular disease
• Paget's disease of the breast
• Prior history of DCIS or invasive breast cancer
• Prior breast or thoracic radiation therapy (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
• Positive axillary node(s)
• T stage of T2 with the tumor > 3 cm in maximum diameter or a T stage >= 3
• Estrogen receptor negative and progesterone receptor negative tumor
• Any of the dosimetric treatment criteria as defined have not been met; patients who become ineligible due to inability to meet dosimetric criteria should not receive treatment as defined in this protocol and will come off the study; any subsequent adjuvant radiation will be delivered at the discretion of the treating physician