Reduced Intensity Versus Myeloablative Allogeneic Hematopoietic Cell Transplant for Chronic Myelomonocytic Leukemia: A Single Institution Experience

Background Allogeneic hematopoietic cell transplant (alloHCT) is the only potentially curative therapy for CMML. Outcomes after alloHCT for higher-risk CMML remain very poor, with 5-year overall survival (OS) of 27%. Given age, comorbidities, and often advanced disease, patient selection and the optimal timing of transplant can be challenging. We undertook this analysis to investigate our institutional experience with alloHCT for CMML. Methods We conducted a retrospective analysis was performed on patients who received alloHCT at the Cleveland Clinic between January 1, 2010 and April 1, 2023. Patients with a diagnosis of CMML were included. All donor types and graft sources (peripheral blood stem cells, bone marrow, cord blood) were included. Results A total of 33 patients were identified. Median age at time of transplant was 63 (range, 41-74), with greater than half (n=18, 54.5%) age 65 or older. Males represented 75% of the cohort. The median time from CMML diagnosis to alloHCT was 0.8 years (range, 0.36-21.2). The majority of transplants were reduced intensity (n=22, 66.7%). Peripheral blood stem cells were used in most transplants (n=24, 72.7%), with a minority from bone marrow (n=8, 24.2%) and multiple cord blood in (n=1, 3%). Incidence of any-grade acute and chronic GVHD was 48.5% and 27.3%, respectively. Median OS (mOS) from time of diagnosis was 5.5 years, and from time of transplant was 1.62 years. At median follow-up time of 1.04 years, OS was 63.6% (n=21). Elderly patients (≥65) had a median survival post-transplant of 1.2 years, versus 3.15 years for those <65 (p=0.37). Myeloablative transplant, most commonly with Bu/Cy conditioning, had a mOS from transplant of 3.16 years, versus 1.05 years for reduced-intensity transplant (p=0.37). Five year OS was 30% (Figure 1). Relapse accounted for 45% (9/20) of deaths; 8 of these patients received RIC. Discussion Our institutional 5-year OS post-alloHCT of 30% is similar to that reported in the literature. Elderly patients (≥65) with CMML and those who received a reduced intensity allogeneic transplant had a markedly reduced mOS from the time of transplant (Figure 2). Analysis against patients who did not undergo transplant, and investigation of molecular mutational status of the patients, is planned. Strategies to reduce relapse and optimize patient selection need to be considered.