Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed locally recurrent breast carcinoma consistent with the
following cell types:

- Invasive ductal breast carcinoma

- Medullary ductal breast carcinoma

- Tubular ductal breast carcinoma

- Mucinous ductal breast carcinoma

- Lobular breast carcinoma

- Ductal carcinoma in situ (DCIS)

- No Paget disease of the nipple

- Initial lumpectomy followed by whole-breast radiotherapy performed over 1 year ago

- Repeat lumpectomy performed within the past 42 days

- Target lumpectomy cavity must be clearly defined and the target lumpectomy cavity/
whole-breast reference volume must be < 30% based on a post-operative, pre-treatment
CT scan

- Histopathologic confirmation via lumpectomy of local in-breast ipsilateral recurrence
within the past 120 days and the following must be true:

- Tumor size ≤ 3 cm in greatest dimension on pathologic specimen

- Negative histologic margins of resection and no tumor on ink following
breast-preserving surgery

- Re-excision to achieve negative margins allowed

- Axilla negative or ≤ 3 positive lymph nodes without extracapsular extension

- If the in-breast recurrence is DCIS and/or microinvasive disease, a sentinel lymph
node (SLN) evaluation is not required, but if performed:

- Patients with a negative sentinal lymph node (SLN) biopsy are eligible for
enrollment

- Patients with a positive SLN biopsy require an axillary lymph node (ALN)
dissection (ALND is not required if the SLN is not identified)

- Patient is eligible if 0-3 positive ALNs without extracapsular extension is
documented

- If the in-breast recurrence is invasive disease and:

- No prior ALN dissection or SLN dissection only:

- Patient is required to undergo axillary evaluation with either a SLN or ALN
dissection

- If the SLN is not identified or if the SLN is positive for metastatic
disease then an ALN dissection is required

- Patient is eligible for enrollment if encounter 0-3 positive lymph nodes
without extracapsular extension

- • Prior ALN dissection: negative clinical exam: patient is eligible for
enrollment

- It is recommended, but not required, that the patient undergo ultrasound
evaluation of the axilla and the lymph node draining regions of the breast;
any suspicious areas are to be biopsied and if positive followed with an
ALN dissection

- Patient is eligible for enrollment if biopsies are negative or 0-3 axillary
lymph nodes without extracapsular extension are encountered

- Prior ALN dissection: positive clinical exam: biopsy required

- If biopsy is negative, patient is eligible for enrollment

- If biopsy is positive an ALN dissection is required

- Patient is eligible for enrollment if biopsies are negative or 0-3 axillary
lymph nodes without extracapsular extension encountered

- Ipsilateral breast mammogram and MRI within 120 days prior to study entry

- Contralateral breast mammogram within 12 months of study entry

- No more than 120 days since whole-body PET-CT scan OR CT scan of the chest, abdomen,
and pelvis, and bone scan

- No multicentric ipsilateral breast recurrence or regional recurrence (other than
axilla)

- Patients must have a breast technically amenable to partial-breast irradiation

- No metastatic disease documented by physical exam or radiographic evaluation (for
patients with invasive disease)

- No skin involvement

- No prior contralateral mastectomy

- Estrogen and progesterone status must be known

PATIENT CHARACTERISTICS:

- Zubrod performance status 0-1

- Menopausal status not specified

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No other invasive malignancy within the past 3 years except ipsilateral breast cancer
and/or nonmelanoma skin cancer

- No collagenous diseases, specifically systemic lupus erythematosus, scleroderma, or
dermatomyositis

- No psychiatric or addictive disorders that would preclude obtaining informed consent

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- More than 2 weeks since prior chemotherapy and recovered

- No concurrent intensity-modulated radiotherapy

- No concurrent chemotherapeutic agents, including trastuzumab