OBJECTIVES: I. Estimate the maximum tolerated dose of continuous infusion interleukin-2 (IL-2) that can be combined with a standard dose of filgrastim (G-CSF) to stimulate peripheral blood stem cells (PBSC) for harvest in patients with advanced breast cancer. II. Assess PBSC engraftment following high dose cyclophosphamide, thiotepa, and carboplatin (the STAMP V regimen) supported by G-CSF or IL-2/G-CSF hematopoietic support in patients who underwent the same pretransplant PBSC stimulation. III. Characterize the toxic effects of combined IL-2 and G-CSF. IV. Compare immune function changes following IL-2/G-CSF and G-CSF alone by assessing expression of CD56/CD56-bright, CD3, and CD25; natural killer cell and lymphokine activated killer cell activity; T-cell responses (TT, HER2/neu); and serum levels of interleukin-6, tumor necrosis factor, and G-CSF. V. Compare the effects on the expression of circulating hematopoietic progenitor cells (CD34+, CFU-GM, and BFU-GM) of a range of IL-2 doses when combined with G-CSF to those achieved with G-CSF alone. VI. Compare the time to neutrophil and platelet recovery, requirements for red blood cell and platelet transfusion, and time to hospital discharge in patients receiving IL-2/G-CSF-primed vs. G-CSF-primed PBSC following STAMP V chemotherapy. VII. Compare the feasibility, toxicity, and hematologic and immunologic effects of post-PBSC infusion of IL-2/G-CSF vs. G-CSF alone. VIII. Assess the response rate, duration of response, and disease free interval of patients with advanced breast cancer treated with STAMP V with PBSC rescue. IX. Assess the presence of cytokeratin as a marker of minimum residual disease when measured in blood and marrow by polymerase chain reaction during and following treatment.