Radiation Therapy Using Gold Markers in Treating Women With Early-Stage Breast Cancer

DISEASE CHARACTERISTICS: Inclusion criteria: * Histologically confirmed ductal carcinoma in situ or invasive carcinoma of the breast (including ductal, medullary, papillary, colloid \[mucinous\], or tubular histologies) meeting all of the following criteria: * AJCC stage 0, I, or II (Tis, T1N0, or T2N0) disease with a lesion ≤ 3 cm treated with lumpectomy and either sentinel node biopsy or axillary dissection (if invasive carcinoma is present) * Unifocal breast cancer (i.e., single focus that can be encompassed by one lumpectomy) * Underwent or plan to undergo lumpectomy with placement of gold fiducial markers (markers placed concurrently with the surgery or on a later date) * Patients who has underwent lumpectomy must meet all of the following criteria: * Must be enrolled between 14-60 days from date of last surgery, and radiation must start within 15-80 days of date of last surgery * Four to six gold fiducial markers placed in the tumor bed, delineating the margins of the lumpectomy cavity * Negative, inked histologic margins of lumpectomy (\> 1 mm) or re-excision specimen to be confirmed prior to radiation * Margins are unacceptable if there is invasive or non-invasive tumor within 1 mm of the inked margin * Negative post-excision mammography if malignancy-associated microcalcifications were initially present * Hormone receptor status not specified Exclusion criteria: * Evidence of suspicious microcalcifications in the breast prior to the start of radiation * One or more positive axillary nodes or positive sentinel biopsy * Distant metastases * Invasive or extensive in-situ lobular carcinoma or non-epithelial breast malignancies such as sarcoma or lymphoma * Proven multicentric carcinoma (tumors in different quadrants of the breast or tumor separated by at least 4 cm) with other clinically or radiographically suspicious areas in the ipsilateral breast unless confirmed to be negative for malignancy by biopsy * Palpable or radiographically suspicious contralateral axillary, supraclavicular, infraclavicular, or internal mammary nodes, unless there is histologic confirmation that these nodes are negative for tumor * Paget's disease of the nipple * Skin involvement, regardless of tumor size PATIENT CHARACTERISTICS: * Female * Menopausal status not specified * ECOG performance status 0-1 * Life expectancy ≥ 2 years * Not pregnant or nursing * No prior treated breast carcinoma within the past 5 years * No collagen vascular diseases, specifically systemic lupus erythematosus, scleroderma, or dermatomyositis * No co-existing medical conditions * No patients with medical conditions that would preclude compliance with the trial, as determined by the investigator * No other malignancy, except non-melanomatous skin cancer, within the past 5 years * Disease-free interval from any prior carcinoma must be continuous * No breast technically unsuitable for radiotherapy PRIOR CONCURRENT THERAPY: * See Disease Characteristics * Concurrent tamoxifen citrate, anastrozole, or other hormonal therapy allowed * Future chemotherapy allowed provided it is administered after the APBI and begins no earlier than 2 weeks after completion of radiotherapy * No tylectomies so extensive that the cosmetic result is low or poor prior to radiation * No prior radiation to the ipsilateral breast * No prior non-hormonal therapy or radiotherapy for this disease * No chemotherapy in the past 2 weeks * No concurrent chemotherapy, immunotherapy, or experimental medications