P1277: impact of a novel prognostic model on allogeneic haematopoietic stem cell transplantation outcomes in patients with cmml

Topic: 22. Stem cell transplantation - Clinical Background: Chronic myelomonocytic leukaemia (CMML) is a clonal haematopoietic stem cell malignancy, and allogeneic haematopoietic stem cell transplantation (allo-HSCT) is a potentially curative treatment option. The outcomes after transplant are influenced by both disease- and patient-related factors. Aims: Develop a novel prognostic model to predict post-transplant survival for CMML patients. Methods: A prognostic model was developed from the univariable and multivariable Cox proportional hazards regression models. Results: The analysis included 218 CMML patients treated with allo-HSCT from 27 centres in China from 2005 to 2022. We identified risk factors by applying univariable and multivariable Cox proportional hazards regression to a derivation cohort of 119 patients. In multivariable analysis, advanced age (hazard ratio [HR] 3.583), leukocyte count (HR 3.499) and anaemia (HR 3.439) at initial diagnosis, bone marrow blast cell count before transplant (HR 2.095), and no cGVHD after transplant (HR 4.799) were independently associated with worse survival. Accordingly, a novel prognostic model termed ABLAG (Age, Blast, Leukocyte, Anaemia, cGVHD) was developed based on the regression equation, and the following points were assigned: 1 point for age > 60 years, blasts > 10%, leukocyte counts > 32×109/L or haemoglobin≤120 g/L and 2 points for no cGVHD. The CMML prognostic model (range, 0-6) was predictive of survival and non-relapse mortality (NRM) (P<0.001 for both), and the patients were stratified into 3 risk groups: low risk (0-1), intermediate risk (2-3), and high risk (4-6). Three risk groups were identified, with a 3-year survival of 93.3% for low risk, 78.9% for intermediate risk, and 51.6% for high risk (P<0.001) and a 3-year NRM of 6.1% for low risk, 17.3% for intermediate risk, and 36.8% for high risk (P<0.001). An increasing risk score was also significantly associated with lower progression free survival (PFS) (P <0.001); however, there was no difference in the cumulative relapse rate among the three risk groups (P=0.077). Then, we evaluated the performance of the prognostic model through a bootstrap procedure for internal validation. Furthermore, an external validation with data from a validation cohort consisting of 99 patients from 1 other centre was conducted. The areas under the receiver operating characteristic (ROC) curves for the derivation and validation cohort were 0.829 (95% CI, 0.776-0.902) and 0.749 (95% CI, 0.684-0.854), respectively. Both calibration plots showed that the novel model illustrated a high degree of consistency in the estimated and observed risk compared with existing models designed for the non-transplant setting. Moreover, we generated a decision curve analysis curve to determine whether the model could provide a clinical benefit for CMML patients after allo-HSCT. Compared with previous prognostic scoring models, the novel prognostic model contributed to considerable net benefits. Conclusion: In conclusion, by combining disease- and patient-related factors, this novel CMML prognostic model provides better survival stratification for patients with CMML receiving allo-HSCT and may facilitate personalized counselling. Keywords: Allogeneic hematopoietic stem cell transplant, Prognostic, Chronic myelomonocytic leukemia