A Phase II trial of gemcitabine and mitoxantrone for patients with acute myeloid leukemia in first relapse.

INTRODUCTION We evaluated the complete remission (CR) rate in patients with acute myeloid leukemia (AML) in first relapse treated with fixed-dose-rate gemcitabine and mitoxantrone. In addition, we measured multidrug resistance (MDR) proteins on pretreatment bone marrows and correlated expression with outcome. PATIENTS AND METHODS The study was performed in a 2-stage design. Pretreatment bone marrows were assayed for the MDR proteins (LRP, MDR1, MRP1, SLC28-29A1/A2, ABCC4/C5, and GSTP1) by immunohistochemistry and reverse-transcriptase polymerase chain reaction (RT-PCR). RESULTS Only 5 of the first 24 patients (21%) achieved CR; therefore, the study was terminated. Eleven patients (46%) had poor-risk cytogenetics and the median duration of first CR was 7.3 months. Patients had significant expression of the various MDR genes, with 70% of patients expressing moderate to high levels of GSTP1 by immunohistochemistry. Higher sum total of ABCC4 and SLC29A2 expression measured by RT-PCR was associated with not achieving CR (20.6 vs. 12.1; P = .006). In addition, there was a trend for higher expression of the sum total of the 10 MDR genes (measured by RT-PCR) and not achieving CR (P = .06). CONCLUSION The CR rate in this study was comparable to other regimens used in poor-risk patients. Of interest, ABCC4 and SLC29A2 expression were predictive of achieving CR. The high expression of GSTP1 suggests that this may be a therapeutic target for relapsed AML. Finally, the rapidity and ease of using RT-PCR to quantify MDR in this study may have clinical utility in future trials.