Radiation Therapy in Treating Women With Early Stage Breast Cancer

DISEASE CHARACTERISTICS:

Histologically confirmed breast cancer, including 1 of the following subtypes:

Ductal carcinoma in situ
Invasive ductal carcinoma
Invasive lobular carcinoma
Medullary carcinoma
Papillary carcinoma
Colloidal (mucinous) carcinoma
Tubular carcinoma

Pathological stage 0-IIIA disease (pTis; pT1-2, N0-N2a, M0)

Tumor size ≤ 5 cm
Breast considered technically satisfactory for radiotherapy

Has undergone lumpectomy or mastectomy and either sentinel node biopsy or axillary dissection (if invasive carcinoma is present)

Negative inked histological margins (i.e., no invasive cells at surgical margin) or confirmed negative re-excision specimen
Unifocal or multifocal (confined to 1 quadrant; tumors < 4 cm apart) disease with 1 or 2 foci that can be encompassed by 1 lumpectomy
No proven multicentric carcinoma (tumors in different quadrants of the breast or tumor separated by ≥ 4 cm) with other clinically or radiographically suspicious areas in the ipsilateral breast unless confirmed to be negative for malignancy by biopsy

No evidence of suspicious microcalcifications in the breast before the start of radiotherapy

If malignancy-associated microcalcifications were initially present, the post-excision mammography must be negative
No more than 9 positive axillary lymph nodes
No palpable or radiographically suspicious contralateral axillary, supraclavicular, infraclavicular, or internal mammary nodes unless there is histologic confirmation that these nodes are negative for tumor
No previously treated contralateral breast cancer or synchronous ipsilateral breast cancer
No lobular carcinoma in situ alone (i.e., no invasive component) or non-epithelial breast malignancies (e.g., sarcoma or lymphoma)
No Paget disease of the nipple
No skin involvement, regardless of tumor size
No distant metastases
Hormone receptor status not specified

PATIENT CHARACTERISTICS:

Pre- or post-menopausal
ECOG performance status 0-1
No co-existing medical condition that would limit life expectancy to < 2 years
Not pregnant or nursing
Negative pregnancy test
Fertile patients must use effective contraception
No other malignancy within the past 5 years except for nonmelanoma skin cancer (the disease-free interval from any prior malignancy must be continuous)
No collagen vascular disease, specifically systemic lupus erythematosus, scleroderma, or dermatomyositis
No psychiatric or addictive disorder that would preclude obtaining informed consent

PRIOR CONCURRENT THERAPY:

See Disease Characteristics
No prior radiotherapy for the current breast cancer
No tylectomies so extensive that the cosmetic result is low or poor prior to radiotherapy

Chemotherapy allowed provided the following criteria are met:

Chemotherapy is not administered prior to, during, and for ≥ 21 days after completion of radiotherapy (for patients receiving brachytherapy boost)
Chemotherapy is not administered for ≥ 21 days before, during, and for ≥ 21 days after completion of radiotherapy (for patients receiving external beam radiotherapy boost or chest wall irradiation)

Concurrent tamoxifen, anastrozole, or other hormonal therapy allowed

May be initiated before, during, or after radiotherapy
No other concurrent chemotherapy, immunotherapy, or experimental medications