RATIONALE: Radiation therapy uses high-energy x-rays and other types of radiation to kill tumor cells. Giving radiation therapy in different ways may kill more tumor cells.

PURPOSE: This clinical trial is studying how well partial breast radiation therapy works in treating women undergoing breast-conserving therapy for early stage breast cancer.

OBJECTIVES:

• To determine the cosmetic outcome resulting from partial breast irradiation using two different techniques.
• To determine patient satisfaction with partial breast irradiation as it pertains to their overall treatment experience as measured by a questionnaire.
• To determine if there are patient factors that limit a patient's suitability to receive partial breast irradiation delivered by a particular technique.
• To evaluate wound healing and overall complication rate after partial breast irradiation.
• To determine ipsilateral breast tumor recurrence rates and tumor bed recurrence rates.

OUTLINE: Patients undergo partial breast irradiation comprising either MammoSite® brachytherapy twice daily for 5-10 days OR 3-dimensional conformal radiotherapy twice daily for 5-10 days.

After completion of study therapy, patients are followed periodically for up to 5 years.

DISEASE CHARACTERISTICS:

• Histologically confirmed breast cancer, including the following histologic subtypes:

  • Invasive ductal carcinoma
  • Medullary ductal carcinoma
  • Papillary ductal carcinoma
  • Colloid (mucinous) ductal carcinoma
  • Tubular ductal carcinoma

• The following histologic subtypes are not allowed:

  • Invasive lobular carcinoma
  • Extensive lobular carcinoma in situ
  • Ductal carcinoma in situ (DCIS)
  • Nonepithelial breast malignancies, such as lymphoma or sarcoma

• No extensive intraductal component by Harvard definition (i.e., more than 25% of the invasive tumor is DCIS or DCIS present in adjacent tissue)

• Stage I or II disease (T1, N0; T1, N1a; T2, N0; or T2, N1a)

  • Lesion ≤ 3 cm

  • No more than 3 positive lymph nodes

    • Patients with 4 or more positive axillary lymph nodes found at the time of axillary lymph node dissection/sentinel lymph node biopsy are not eligible

• Has undergone tylectomy (lumpectomy) and axillary lymph node sampling (axillary node dissection or sentinel node biopsy)

  • Negative resection margins with ≥ 2 mm margin from invasive or in situ cancer OR a negative re-excision margin

• Unifocal breast cancer

  • No multicentric carcinoma (tumors in different quadrants of the breast or tumors separated by ≥ 4 cm)

    • No palpable or radiographically suspicious contralateral axillary, ipsilateral or contralateral supraclavicular, infraclavicular, or internal mammary lymph nodes unless these are histologically confirmed negative

• No skin involvement of disease

• No Paget's disease of the nipple

• No distant metastatic disease

• Hormone-receptor status not specified

PATIENT CHARACTERISTICS:

• Female
• Menopausal status not specified
• Not pregnant or lactating
• Negative pregnancy test
• Fertile patients must use effective contraception for ≥ 1 week prior to, during, and for ≥ 2 weeks after completion of study treatment
• No collagen vascular disorders, specifically systemic lupus erythematosus, scleroderma, or dermatomyositis
• No psychiatric, neurologic, or addictive disorders that would preclude obtaining informed consent
• No other malignancy within the past 5 years, except non-melanomatous skin cancer

PRIOR CONCURRENT THERAPY:

• No prior radiotherapy to the breast
• No chemotherapy for at least 2 weeks before and 2 weeks after completion of study radiotherapy
• Concurrent hormonal therapy allowed