Hypoplastic Acute Myeloid Leukemia.

Hypoplastic variant of acute leukemia is rare and almost always has a myeloid phenotype. We retrospectively investigated the incidence, clinico-laboratory characteristics, and clinical outcomes of hypoplastic acute myeloid leukemia (HAML), which was defined by bone marrow hypocellularity (less than 40% of cellularity in trephine biopsy) with increase of bone marrow blasts (20% or more) and peripheral blood leukopenia (less than 4,000/μl). Between 1989 and 2005, 740 patients were diagnosed as having AML at the Asan Medical Center and the definition of HAML was satisfied in 24 (3.3%). Patients with HAML showed a higher median age (67.5 vs. 44.0 years; P<0.001), a higher frequency of CD34 (100% vs 61.7%; P=0.007) and MDR (90% vs. 58%; P=0.043) expression and lower survival rate (6.7% vs 26.7% at 5-year; P=0.035) compared to other AML patients. The age range of 24 HAML patients, 16 males and 8 females, was 19 to 86 years, and 17 patients (70.8%) were 60 years or more. The results of cytogenetic analysis were available in 16 patients: 1 in good risk group, 14 in intermediate risk group, and 1 in poor risk group. Induction chemotherapy was given to 14 patients (58.3%): standard induction chemotherapy with AI or AD regimen (AI/AD) in 9 patients and low-dose cytarabine (LDAC) in 5. Complete remission (CR) was induced in 7 (50.0%) of 14 patients: 44.4% for AI/AD and 60.0% for LDAC. The CR rate was lower in patients with higher LDH over 400 U/L (25.0% vs. 100%; P=0.014). A median overall survival (OS) was 131 days. Seventeen patients died, two were lost to follow up, two were alive without disease, and one was alive with disease. Both patients, who were alive without disease, received allogeneic hematopoietic cell transplantation (HCT). Age (P=0.007) and LDH (P=0.016) were significant prognostic factors for OS. Our results suggest that HAML represents a poor prognostic group of patients. Prospective study is warranted for establishment of optimal treatment strategy including LDAC and HCT.