A phase II study of high-dose cyclophosphamide, thiotepa, and carboplatin with autologous marrow support in women with measurable advanced breast cancer responding to standard-dose therapy.

PURPOSE: The study was designed to determine the duration of complete response (CR) for patients with unresectable or metastatic breast cancer treated with high-dose cyclophosphamide, thiotepa, and carboplatin (CTCb) while responding to conventional-dose therapy. METHODS: Eligibility criteria included histologically documented metastatic or unresectable breast cancer, at least a partial response (PR) to conventional-dose therapy, no prior pelvic radiotherapy, cumulative doxorubicin of less than 500 mg/m3, and physiologic age between 18 and 55 years. Patients with inadequate renal, hepatic, pulmonary, and/or cardiac function or tumor involvement of marrow or CNS were excluded. Cyclophosphamide 6,000 mg/m2, thiotepa 500 mg/m2, and carboplatin 800 mg/m2 were given by continuous infusion over 4 days. After recovery, sites of prior bulk disease were to be radiated or resected if feasible. RESULTS: Of 29 registered patients, one died of toxicity (3%; hemorrhage). CRs and PRs continued a median of 16 and 5 months after transplant, respectively (26 and 9 months from initiation of chemotherapy for metastatic disease). Of 10 patients transplanted in CR, four have not progressed at 17 to 31 months after transplantation (25 to 43 months after beginning standard-dose therapy). One of four patients with uptake on bone scan as their only sites of residual disease before transplant and one of three who converted from PR to CR with transplant have not progressed at 27 and 29 months, respectively, after transplant. CONCLUSIONS: CTCb is an intensification regimen with a low mortality that delivers a significantly increased dose of agents with known activity at conventional doses in breast cancer. Although the duration of PR is short as expected, CRs appear to be durable.