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