Summary:We assessed the effect standard-dose induction chemotherapy and tandem cycles of high-dose chemotherapy (HDC) have on outcomes in metastatic breast cancer. One hundred and one women with metastatic breast cancer were enrolled in two non-randomized phase II studies. The first group of 64 patients (induction group) received four cycles of docetaxel 75 mg/m 2 and doxorubicin 50 mg/m 2 . The next 37 patients did not receive induction (no induction group). Both groups received two (tandem) cycles of HDC. Blood-derived stem cells were collected after the first HDC cycle, processed using CD34 + cell selection and then reinfused after the second HDC cycle. Outcomes were compared between the two groups and also to patients participating in the Philadelphia (inter-group) randomized metastatic breast cancer transplant trial (PBT-01). Intent-to-treat analysis revealed no significant differences in complete response rates (37.5% vs 27%; P = 0.20), overall response (75% vs 71%), median progression free survival (PFS) (11.9 vs 8 months; P = 0.24) and overall survival (OS) (Ͼ36 vs 25 months; P = 0.16), in the induction vs no induction groups, respectively. Adjusting for differences in known baseline characteristics, induction group patients were found to have significantly longer PFS (P = 0.002), OS (P = 0.01) and more frequent conversion from a partial to complete response (58% vs р13%, P р 0.0002) when compared with PBT-01 patients. Induction chemotherapy administered prior to tandem cycles of HDC does not appear to adversely affect outcomes in metastatic breast cancer patients. Outcomes in our induction group also compare favorably with those observed in PBT-01 and warrant further clinical investigation. Chemotherapy agents administered to patients with metastatic breast cancer in standard doses, alone or in combination, result in a low complete response rate (CR) (8-20%), short response duration (median 5-14 months) and limited overall survival (median 14-24 months). 1-3 Several pilot phase II trials using high-dose chemotherapy (HDC) supported by autologous hematopoietic stem cell transplantation appeared to result in superior outcomes, including a greater than expected percentage of patients who were disease-free (7-18%) after 5 years of follow-up. 4,5 However, results from the Philadelphia bone marrow transplant group (inter-group) phase III randomized trial (PBT-01) support the contention that patient selection bias, and not the efficacy of HDC, results in the apparent outcome advantage observed in patients with advanced breast cancer enrolled in HDC trials. [6][7][8][9] In PBT-01, a single cycle of HDC with unpurged stem cell rescue failed to improve survival over standard-dose therapy. This outcome, however, may have been a consequence of several factors. Reports of 2-year disease-free survival rates approaching 60% in two phase II trials of multiple cycles of HDC administered in rapid succession to patients with metastatic breast cancer indicate that one cycle of HDC may not be optimal. 10,11 The superiority ...