Outcomes of Allogeneic Stem Cell Transplant in Patients with Chronic Myelomonocytic Leukemia (CMML) - a Single Institution Experience

Background:

CMML is a clonal hematopoietic stem cell disorder with myelodysplastic and myeloproliferative overlap features and a high tendency to progress to acute leukemia. Although treatment options include supportive care and use of hypomethylating agents, allogenic hemopoietic stem cell transplant (allo HCT) remains the only curative option. We sought to evaluate outcomes in patients with CMML that underwent allo HCT.

Methods:

After IRB approval, consecutive adult patients with CMML who underwent allo HCT from 1990 to 2014 were identified and evaluated. All data were retrospectively abstracted. Conditioning regimens, GVHD prophylaxis and transfusions were according to institutional standards. 

Results:

Thirty-six patients (males 23%) who met WHO criteria for CMML were included. The median age was 53 years (range, 18 to 66 years) and 20 patients (56%) had CMML-1, while 16 patients (44%) had CMML-2. Patient distribution according to Mayo risk category was: 20 high-risk, 9 intermediate-risk and 7 low-risk while distribution according to Spanish karyotype was: 9 high-risk, 7 intermediate-risk and 20 low-risk.

Twenty-two received myeloablative conditioning (median age: 49 years) and 14 received reduced-intensity conditioning (median age: 59 years). At the time of transplant, 20 patients had received induction chemotherapy, 6 had received hypomethylating agents and 10 were managed by supportive care. Twenty-six patients (72%) experienced acute graft-versus-host disease (GVHD) (15 grade II-IV) and 23 (64%) patients experienced chronic GVHD (11 severe). Post-transplant complete remission was achieved in 25 patients (69%). At 1 year follow-up, 16 (44%) patients had died while 18 (50%) had relapse-free survival. Median follow-up was 17 months (range 0.7- 191 months) and at last follow-up, 23 (64%) deaths were documented (8 disease relapse, 13 non-relapse mortality, 2 lost follow-up). Most common causes of non-relapse mortality were complications related to GVHD (31%) and sepsis (31%). In a survival analysis, engraftment failure and high HCT-comorbidity index had a trend towards shortened overall survival.

Conclusions:

Allogeneic HCT remains a viable treatment option for patients with CMML, with engraftment failure and high co-morbidity index being potential poor prognosticators impacting survival. Conventional risk stratifying CMML models did not predict for HCT outcomes.