Presenting clinical and laboratory characteristics
A total of 138 Mayo Clinic patients (62% male) with CMML who underwent ASCT were included in the study (Table 1). The median ages at the time of diagnosis and at the time ASCT were 62 (range 18-75) and 63 (range 18-76) years, respectively. Group A comprised 104 patients, while Group B consisted of 34 patients. All patients underwent transplantation between 1995 and 2024. At initial diagnosis, CMML-1/CMML-2 and MD-CMML/MP-CMML phenotypes were seen in 78%/22% and 54%/46% of patients, respectively. Among patients with available molecular data (n=86), the most frequent mutations/variants were ASXL1 (56%), TET2 (44%), and SRSF2 (38%). Abnormal karyotypes were observed in 31% of patients. CPSS-Mol risk categories at diagnosis were low (17%), intermediate-1 (11%), intermediate-2 (40%), and high (32%). BLAST score categories were low risk (38%), intermediate risk (44%), and high risk (18%). Compared to Group B, patients in Group A were more likely to present with RUNX1 mutations/variants (24% vs 0%; p=0.01) and more often received pre-transplant HMA (64% vs 36%; p=0.01). In contrast, Group B patients more frequently received intensive chemotherapy prior to ASCT (79% vs 13%; p=0.01). Other clinical and laboratory characteristics are summarized in Table 1.
Pre- and Peri-Transplant Treatment and Disease Status
HMAs were used as first-line CMML-directed therapy in 75 (60%) patients, intensive chemotherapy in 29 (23%), other therapies (including hydroxyurea, erythropoietin agonist, danazol, ruxolitinib, or clinical trials) in 16 (13%), and no treatment in 5 (4%; Table 1). Twenty-nine (21%) patients received two or more lines of cytotoxic therapies.
Bone marrow assessment at the time of ASCT was available in 126 (91%) patients. In Group A, BM blasts were <5% in 76 (80%), 5-9% in 15 (16%) and 10-19% in 4 (4%) patients. In Group B, BM blasts were <5% in 26 (85%), 5-9% in 2 (6%) and 10-19% in 2 (6%; Table 2) patients. Among patients with BM blasts <5%, abnormal cytogenetics were observed in 20 (30%) patients in Group A and 6 (30%) in Group B. Median KPS score prior to transplant was 90 in both Group A (range: 50-100) and Group B (range: 70-100). HCT-CI scores were 0-1 in 42%, 2-3 in 41%, and ≥4 in 16% of patients.
Donor types included matched unrelated (MUD; 58%), matched sibling (MSD; 25%), mismatched unrelated (MMUD; 7%), haploidentical (Hapolo; 9%), and cord blood (1%). RIC was used in 99 patients (73%) and MAC in 36 (26%). Specifically, 17 (13%) patients received busulfan-based MAC, 15 (12%) received cyclophosphamide with total body irradiation (Cy-TBI) MAC, 21 (16%) received busulfan-based RIC, 64 (49%) received melphalan-based RIC, 9 (7%) received Fludarabine-Cy-TBI based RIC (Flu/Cy/TBI), and 4 (3%) received other regimens. GVHD prophylaxis was methotrexate-based in 84 patients (64%) and PTCy-based in 39 (30%). The median donor age was 30 years (range 13-73), and 57% of donors were male (Table 2). Among the 39 patients who received PTCy, 21 (54%) patients received stem cells from MUD, 12 (30%) from Haplo, 5 (13%) from MMUS and 1 (3%) from MSD. In the same group, RIC was used in 35 (90%) and MAC in 4 (10%) patients.
Post-transplant survival and risk factors
Among 138 patients, 68 (49%) had died at the time of censoring. The median follow-up duration was 71 months (range, 3-212). The median time from diagnosis to ASCT was 11 months (range: 0-201). The median OS from the time of initial diagnosis was 67 months (range, 8-239), and the median PTSwas 54 months (range: 0-212), with 1-, 3-, and 5-year PTS rates of 74%, 57%, and 48%, respectively (supplementary table 1). The median RFS was 34 months, with 1-, 3-, and 5-year RFS rates of 66%, 49%, and 42%, respectively (supplementary table 1). Group B patients had significantly worse PTS compared with those in group A (16 vs 95 months; P=0.01; HR 1.9, 95% CI 1.2-3.2; figure 1).
In group A, the median PTS was 95 months (range, 0-212), with 1-, 3-, and 5-year PTS rates of 79%, 62%, and 54%, respectively. The median RFS was 54 months, with 1-, 3-, and 5-year RFS rates of 71%, 52%, and 46%, respectively (supplementary figure 1). In univariate survival analysis (UVA), BM blasts at the time of ASCT of <5%, 5-9%, and 10-19% were associated with median OS of 164, 69 (HR 1.8), and 13.5 (HR 4.3) months, respectively (p=0.01, figure 2a).
Group A Patients who received two or more lines of cytotoxic therapies had inferior PTS (median 11 months) compared to those treated with one line (69 months; HR 3.6) or those who did not receive any cytotoxic drugs (95 months; HR 4.6; p=0.01; supplementary figure 2a). Additional factors associated with inferior PTS included abnormal cytogenetics at diagnosis (p=0.02; HR 1.9, 95% CI 1.06-3.6; figure 2c), and pre-ASCT exposure to HMA (p=0.03; HR 2.03, 95% CI 1.02-4; figure 3a).
PTS was longest in Group A patients who received busulfan-based MAC and shortest in those who received Flu/Cy/TBI-based conditioning (median not reached vs 22 months; p=0.2; supplementary figure 3A). Compared to other GVHD prophylaxis strategies, PTCy was associated with a shorter median PTS (22 vs 107 months; p=0.1; figure 4a) and significantly higher cumulative incidence of relapse (p=0.02; figure 4b). Group A patients who are in complete morphologic remission (CR) at day100 post-ASCT had better PTS (median 164 vs 18 months; p=0.01, HR 0.2, 95% CI: 0.1–0.5; figure 5a). PTSwas worse in patients with aGVHD grade 2-4 compared to those with grade ≤1 aGVHD (median 21 vs 164 months; p=0.01; HR 2.6, 95% CI: 1.4–4.9; figure 6a). Chronic GVHD of any grade confers better PTS (median 164 vs 26 months; p= 0.01; HR 0.3, 95% CI: 0.1–0.6; figure 6b). We found no association between donor type, age, gender and PTS.
Multivariable Cox regression model including BM blasts at the time of ASCT and at day-100 post-ASCT, number chemotherapeutic lines before transplant, cytogenetics at diagnosis and day-100 post-ASCT, pre-ASCT exposure to HMA, conditioning regimen, GVHD prophylaxis, acute GVHD and chronic GVHD identified abnormal cytogenetics at day 100 (p=0.01, HR 5.4, 95% CI: 2.1–13) and aGVHD grade 2-4 (p=0.01, HR 3.6, 95% CI: 1.5–8) to be independently associated with inferior PTS.Conversely, BM blasts <5% at the time of ASCT (p=0.03, HR 0.4, 95% CI: 0.1–0.9) and at day-100 post-ASCT (P=0.08, HR 0.3, 95% CI: 0.8–1.1), and chronic GVHD of any grade (p=0.01, HR 0.2, 95% CI: 0.1–0.5) were independently associated with improved PTS in group A patients.
In group B, median PTS was 16 months (range 0-204), with a 1-, 3- and 5-year PTS rates of 57%, 39% and 29%, respectively. The RFS was 10 months, with a 1-, 3- and 5-year RFS rates of 49%, 38% and 29%, respectively. In univariate analysis, relapse at day-100 post ASCT correlated with worse PTS (median 11 vs 39 months; p=0.01, HR 5.3, 95%CI 1.4-20; figure 5b). PTS was longer with BM blasts of <5% compared to BM blasts >5% at the time of ASCT (median 30 vs 18 months), although this difference was not statistically significant (p=0.4; figure 2b). In group B patients, cGVHD of any grade led to a better PTS (30 vs 18 months; p=0.5). In multivariable analysis, BM blasts at day-100 post-ASCT (p=0.01, HR 0.09, 95%CI 0.01-0.4) was independently associated with better PTS.
At last follow-up, 46 patients (44%) in group A and 22 (64%) in group B were dead. The causes of death were relapse/non-relapse related in 36/64% in group A and 39/61% in group B, respectively (supplementary table 1). The most frequent documented causes of non-relapse mortality were GVHD in 12 (30%) patients, infections in 9 (23%), bleeding in 4 (10%) and solid organ malignancy in 4 (10%).
Graft-versus-host disease and Graft-versus-host disease-free, relapse-free survival
Grade ≥2 aGVHD and moderate to severe cGVHD occurred in 44% and 30% of Group A patients and in 47% and 26% of Group B patients, respectively. Skin was the most frequently involved organ in aGVHD, occurring in 60 (43%) patients, followed by the gut in 44 (32%) and the liver in 18 (13%). Similarly, for cGVHD, skin was most frequently involved occurring in 31 (22%) patients, followed by ocular and oral in 20 (20% each), lung in 22 (16%), liver in 20 (15%), and gut in 10 (7%).
In Group A, the median GRFS was 239 days, with 1-, 3-, and 5-year GRFS rates of 41%, 21%, and 16%, respectively (supplementary table 1). MAC was associated with significantly better GRFS compared to RIC (median 622 vs 206 days; p=0.02, HR 2.1, 95% CI: 1.2–3.7; supplementary figure 4a). In contrast, abnormal cytogenetics (median 130 vs 282 days; p=0.01, HR 2.6, 95% CI: 1.3–5.4; supplementary figures 4c) and BM blasts of >5% at day-100 post-ASCT (median 94 vs 245 days; p=0.01, HR 4.3, 95% CI: 1.5–12.0, supplementary figure 4e) were significantly associated with shorter GRFS. All these variables remained statistically significant in multivariable analysis (p=0.01 in all instances).
In Group B, the median GRFS was 169 days, with 1-, 3-, and 5-year GRFS rates of 30%, 16%, and 16%, respectively. Mixed chimerism at day 100 post-ASCT was associated with significantly shorter GRFS compared to full donor chimerism (median 97 vs 195 days; p=0.01, HR 5.3, 95% CI: 1.3–22.0). Similarly, BM blasts of >5% at day-100 demonstrated a trend toward inferior GRFS (97 vs 195 days; p=0.05, HR 2.8, 95% CI: 0.9–8.9; supplementary figure 4f).