High-dose gemcitabine, busulfan, and melphalan for autologous stem-cell transplant in patients with relapsed or refractory myeloma: a phase 2 trial and matched-pair comparison with melphalan

Summary Background High-dose melphalan is of little benefit as a regimen for patients with relapsed or refractory myeloma undergoing an autologous stem-cell transplant (ASCT). The poor performance of single-agent melphalan in this setting prompted us to study a new high-dose combination of infused gemcitabine, busulfan, and melphalan. Methods We did a phase 2 trial at the University of Texas MD Anderson Cancer Center (Houston, TX, USA). We enrolled patients with primary refractory or relapsed myeloma who had received treatment with bortezomib, an immunomodulatory drug, or both, or who were receiving a salvage ASCT. Gemcitabine was infused at 1875 mg/m2 for 3 h for 2 days, followed by busulfan (target area under the curve 4000 μmol/L per min per day for 4 days) and melphalan (60 mg/m2 per day for 2 days). The primary endpoint of this trial was to establish the proportion of patients with measurable disease at ASCT receiving gemcitabine, busulfan, and melphalan who achieved stringent complete remission in accordance with the International Myeloma Working Group criteria. We then retrospectively compared the patients in this study with all other concurrent patients at the MD Anderson Cancer Center who were eligible for this trial but declined to participate or had no financial coverage for ASCT in a clinical trial and instead received melphalan at 200 mg/m2 intravenously over 30 min on 1 day, followed by ASCT (control group). To compare survival outcomes, we used a statistical algorithm to select a subset of patients from this control cohort who were matched in a 1–2:1 ratio with the patients in the gemcitabine, busulfan, and melphalan group by sex, age, disease status, refractory to both proteasome inhibitors and immunomodulatory imide drugs, time from diagnosis to ASCT, and cytogenetic risk. All analyses were per protocol. This is the final analysis of the clinical trial, which is registered at ClinicalTrials.gov , number NCT01237951. Findings Between Nov 30, 2010, and Dec 11, 2013, we enrolled 74 patients into the gemcitabine, busulfan, and melphalan trial. In these patients, median age was 58 years (IQR 51–62), median number of previous lines of therapy was two (2–5), 38 patients had high-risk cytogenetics, 17 were unresponsive to all previous treatments, and 32 were receiving a salvage ASCT. We identified 184 patients for the concurrent control cohort. The study patients and the concurrent controls received similar post-ASCT maintenance. Among patients wi