DISEASE CHARACTERISTICS:

          -  Histologically confirmed invasive breast carcinoma

          -  Primary operable breast cancer that was surgically treated by wide local excision or
             mastectomy with clear margins (> 1 mm apart from deep margin if full thickness
             resection)

               -  No more than 8 weeks since prior definitive surgery

          -  Early-stage disease with no evidence of metastases clinically or on routine staging
             investigations

               -  No T4 and/or N3 disease

          -  Prior axillary staging required, including 1 of the following:

               -  Sentinel node biopsy

               -  Axillary sampling or clearance

                    -  All node-positive patients must have had axillary clearance or radiotherapy
                       to the axilla

          -  Must be at high risk of relapse within 5 years (risk factors evaluated at clinician's
             discretion)

          -  No other invasive breast cancer, systemically treated ductal carcinoma in situ (DCIS),
             or solid tumor within the past 5 years

          -  No prior hematologic malignancy or melanoma

          -  Hormone receptor status:

               -  Estrogen receptor (ER)- or progesterone receptor (PR)-negative OR ER/PR-weakly
                  positive (e.g., Allred/Quick score ≤ 5 OR H score ≤ 100)

        PATIENT CHARACTERISTICS:

          -  Female

          -  Postmenopausal

          -  Performance status 0-1

          -  Hemoglobin > 9 g/dL

          -  WBC > 3,000/mm³

          -  Platelet count > 100,000/mm³

          -  Bilirubin normal (unless known Gilbert's disease is present)

          -  Albumin normal

          -  AST and ALT ≤ 1.5 x upper limit of normal (ULN)

          -  Creatinine ≤ 1.5 x ULN

          -  Creatinine clearance > 50 mL/min

          -  No active or uncontrolled infection

          -  Must be available for routine long-term hospital follow-up

          -  Must have normal cardiac function and no significant cardiac disease by ECHO or MUGA

        PRIOR CONCURRENT THERAPY:

          -  See Disease Characteristics

          -  At least 4 weeks since prior preoperative endocrine therapy

          -  No prior systemic therapy for this breast cancer or mantle radiotherapy

          -  No prior breast-conserving surgery in which there is a contraindication for, or
             decline of postoperative radiotherapy

          -  No concurrent hormone replacement therapy (HRT)