Partial Breast Radiation Therapy in Treating Women Undergoing Breast Conservation Therapy for Early-Stage Breast Cancer

DISEASE CHARACTERISTICS:

Women who have chosen to undergo breast conservation therapy, including lumpectomy and breast irradiation, at the University of Pennsylvania for any invasive mammary carcinoma or intraductal breast cancer

Stage I-II invasive or intraductal breast cancer

Unifocal tumor ≤ 3.0 cm in size

Patients with microscopic multifocality are eligible provided total pathologic tumor size is ≤ 3 cm

No proven multicentric carcinoma in more than 1 quadrant or separated by 4 or more centimeters

Pre- or post-biopsy ipsilateral* breast MRI negative for multicentric disease (i.e., areas of cancer that cannot be removed in a single excision specimen) or other suspicious findings NOTE: *Patients with synchronous bilateral breast cancers who will be treated with radiotherapy to each breast are eligible, provided such treatment can be performed in a manner that avoids overlap between treatment fields. Both sides may be treated with partial breast irradiation (PBI) if the pathologic eligibility criteria are met for both tumors, or only one side may be treated with PBI if the criteria are met for only one tumor.
Negative margins of excision (≥ 2 mm) OR no tumor seen in a re-excision specimen
No extensive intraductal component present

Negative sentinel lymph node (SLN) or axillary lymph node dissection OR fewer than 4 positive nodes on adequate axillary lymph node dissection (i.e., 10 or more lymph nodes removed)

If a SLN is positive on hematoxylin and eosin (but not by immunohistochemistry alone), complete axillary lymph node dissection is required

Axillary lymph node staging is not required for patients with ductal carcinoma in situ
No SLN identified in the internal mammary nodes
No node > 2 cm
No node with extracapsular extension

Surgical clips placed in the operative bed OR ability to visualize operative bed on CT scan of the breast

Target lumpectomy cavity/whole breast reference volume must be ≤ 30% based on the treatment planning CT scan

No diffuse calcifications on diagnostic mammogram

Negative post-biopsy mammogram required if presented with mammographically detected microcalcifications
Hormone receptor status unspecified

PATIENT CHARACTERISTICS:

Female
Menopausal status not specified

History of non-breast malignancies allowed provided patients have been disease free for 5 or more years prior to randomization and are deemed by their physician to be at low risk for recurrence

Treated carcinoma in situ of the cervix, carcinoma in situ of the colon, melanoma in situ, or basal cell and squamous cell skin cancer within the past 5 years allowed
Patients must agree to undergo breast MRI
No contraindication to MRI, including a pacemaker or other foreign body
Not pregnant or nursing
No technical impediment to appropriate dosimetry
No personal history of collagen vascular disease

PRIOR CONCURRENT THERAPY:

See Disease Characteristics
No prior in-field irradiation
No presence of breast implant
No breast reconstructive surgery prior to study entry
No prior neoadjuvant chemotherapy or hormonal therapy