Tandem peripheral blood progenitor cell transplants as initial therapy for metastatic breast cancer

To investigate the use of two sequential courses of high-dose chemotherapy and peripheral blood progenitor cell (PBPC) transplant as initial therapy for patients with untreated metastatic breast cancer. The goal of the study was to maximize treatment intensity through the use of two non-cross-resistant regimens, each equal in intensity to that used in single transplants.

PBPC were collected after a course of granulocyte colony-stimulating factor (G-CSF) only or of cyclophosphamide, etoposide, and G-CSF. The first transplant regimen consisted of thiotepa (600 mg/m2), cyclophosphamide (6000 mg/m2), and carboplatin (800 mg/m2). After recovery from the first transplant, responding patients received a second course of therapy consisting of busulfan (16 mg/kg) and etoposide (60 mg/kg).

Forty-four patients were enrolled. Five patients did not proceed to transplantation due to tumor progression during PBPC mobilization. Five patients achieved complete response after the first transplant, and 14 were in complete remission at the end of the therapy. Six patients remain free of disease after a median followup of 22 months (range 12-27+ months). The 2-year event-free survival for complete responders is 25.4% (standard error 14.4%). Engraftment was prompt, with a median of 8 and 13 days, respectively, to reach a neutrophil count of 500/mm3 and a platelet count of 50,000/mm3. As a result of the gastrointestinal toxicity of the first course, the median interval between transplants was 68 days. The toxicities of the second transplant course were principally hepatic and muco-cutaneous. Hepatic veno-occlusive disease occurred in 12 patients and was a contributor to the death of three.

Rapid hematologic recovery achieved with PBPC made possible the administration of two courses of high-dose chemotherapy without compromising the intensity of either transplant regimen. The adverse effects of the second course, however, were substantially higher than predicted. The outcome of patients achieving a complete response is promising. Overall, the antitumor benefit of this approach in patients with previously untreated metastatic disease was not superior to that achieved with single transplants in patients responding to standard-dose chemotherapy.