High-dose thiotepa and melphalan with hemopoietic progenitor support following induction therapy with epirubicin-paclitaxel-containing regimens in metastatic breast cancer (MBC)

Background: Preliminary data from phase III randomized studies have failed to show benefit of HDC given as consolidation after anthracycline and alkylating-based chemotherapy in metastatic breast cancer (MBC). Moderate activity of induction regimens and selection of chemoresistant clones are among the possible reasons for these disappointing results. We therefore have designed a phase II study where high-dose alkylating agents are given as consolidation after an induction treatment including the most active agents (epirubicin and paclitaxel) without alkylating agents. Patients and methods: Patients with MBC not previously treated with chemotherapy for metastatic disease were eligible. After six courses of epirubicin-paclitaxel±gemcitabine patients received a course of thiotepa 600 mg/m² + melphalan 160 mg m² with hemopoietic support. Pharmacokinetic parameters of thiotepa and melphalan were measured and related to treatment outcomes. The L-VEF of the patients was monitored before and after treatment. Results: Forty-eight patients have been treated. Before HDC 14 patients were in CR, and 34 in PR. A median of 6.92 × 10⁶ (range 1.53-16.6) CD34+ cells/kg were reinfused after HDC. Median days (range) to neutrophils > 0.5 × 10⁹/l and platelets > 20,000 × 10⁹/l were 9.5 (9-33) and 10 days (9-32), respectively. Symptomatic CHF was observed in two patients (4.1%). C_max and AUC of thiotepa showed a linear relationship with time to progression (TTP) and overall survival (OS): r²=0.6. After HDC the conversion rate from PR to CR was 44.1%. At five years progression-free and overall survival rates are 37.5% and 65%, respectively. A treatment-related death was observed. Conclusions: High-dose thiotepa and melphalan after an epirubicin-paclitaxel-containing treatment is feasible, devoid of significant cardiotoxicity and very active. Pharmacokinetic parameters of high-dose thiotepa might be linked to treatment outcome.