Clinical Research Directory

DISEASE CHARACTERISTICS: * Pathologically proven invasive ductal carcinoma of the breast * Stage I or II disease (pathological tumor size ≤ 3 cm, N0, M0 disease) * No T2 (tumor size \> 3 cm) or T3 disease * No lymph node (L0) or hemangiosis (V0) invasion * Unilateral, unifocal, and unicentric tumor without associated suspicious diffuse microcalcification in the ipsilateral or contralateral breast * No multifocal/multicentric disease * Previously treated with breast-conserving surgery with adequate axillary node management * Negative surgical resection margins for tumor (invasive tumor or ductal carcinoma in situ \[DCIS\]) on histology * Clearly identified primary tumor excision cavity (clips recommended) with a target lumpectomy cavity/whole breast ratio quantifiable and ≤ 25% on the post-operative CT scan * Patients with a lumpectomy cavity/whole breast ratio 25-30% are eligible but will undergo partial breast irradiation using multi-catheter interstitial brachytherapy during study * Breast size amenable to partial breast irradiation (i.e., \> A-cup size) * No other pathological invasive tumor or DCIS * No associated extensive DCIS component (\< 25%) * No associated Paget's disease of the nipple * Hormone receptor status not specified PATIENT CHARACTERISTICS: * Menopausal status not specified * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No breast implants * No collagen vascular disease * No psychiatric condition or other condition that, in the opinion of the investigator, would preclude study requirements PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior radiotherapy * No concurrent chemotherapy * Sequential chemotherapy allowed * Concurrent hormonal therapy allowed