Development of a Modified Prognostic Index for Adult Patients with Acute Lymphoblastic Leukemia

Background:Acute lymphoblastic leukemia (ALL) is associated with inferior overall survival (OS) and progression-free survival (PFS) in adults due to biologic factors and lower tolerance to chemotherapy 1,2. Prognostic stratification is essential to guide therapy intensification and indication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Recently, a prognostic index 2 integrating measurable residual disease (MRD), white blood count (WBC) and cytogenetic/molecular subtypes has been validated in children and young adults with ALL. However, in adult patients, age, allo-HSCT, other genetic subtypes 3 and center reality, may also play role in prognosis. To incorporate new variables to the pre-established prognostic index 2, a multicenter PFS analysis was performed to develop a modified/adpated risk score. Material and Methods: a multicenter (three Brazilian centers and the Spanish PETHEMA AR-03 trial cohort), retrospective study, reviewed medical charts and database of 398 adult patients with Ph-negative ALL (treated between 2003 and 2022), including risk variables: age, WBC count, cytogenetic/molecular classification, MRD, allo-HSCT, clinical outcomes and follow-up. The prognostic index 2 was calculated individually, then through multivariate analysis the coefficients (HR/OR) to incorporate age and allo-HSCT to the model have been determined. The methods of logistic regression, Cox model, Kaplan-Meier, log rank, ROC analysis and competitive risk regression were used in the statistical analysis. Subsequently, patients were stratified into 3 prognostic risk categories. Results: A total of 398 patients, 77% from the PETHEMA protocol and 23% Brazilian centers; 55.2% males; mean age 38.1 years (range 18-60; 67.4% (268) B-ALL; 31.4% (125) T-ALL; 1.2% (5) biphenotypic ALL. median WBC 22.4x10 9/L; 8.9% with central nervous system involvement; 22.9% high risk cytogenetics. Regarding treatment, 93.9% (373) received pediatric-inspired protocols (AR-03, GRAALL, CALGB, St. Jude TOTALXVI), 6.1% (26) (Hypercvad and others). Regarding the response, 83.3% (309/371) achieved complete remission (CR); CR rate was higher in pediatric inspired versus other protocols: 84.6% vs 57.9% (p 0.006). 45.6% (127/278) reached MRD-neg status after induction and 71.4% (125/175) after consolidation; 21.7% (67/309) underwent allo-HSCT in first remission. After a median follow-up of 3.9 years, 4-year-OS was 42.1% (95%CI 47.2-36.8%) and PFS was 33.4% (95%CI 38.5-28.4%). Cumulative incidences of relapse and non-relapse mortality were: 38.0% and 27.6%, respectively. In multivariate analysis, both allo-HSCT (OR:0.36 95%CI 0.19-0.66 p<0.001) and original 2 prognostic index (OR:2.47 95%CI:1.71-3.55 p <0.001) predicted significantly PFS, so allo-HSCT coefficient has been determined and incorporated to the model. According to this modified prognostic index, patients were stratified into 3 risk groups: low (100/285, 35.1%), intermediate (93/285, 32.6%) and high (92/285, 32.3%) high. At 4-years, PFS was significantly superior in low-risk group (55.9% - 95% CI 65.8-44.5%) compared to the intermediate-risk group (37.3% - 95%CI 47.5-27.1%) and high-risk group (182% - 95%CI 27.0-10.8%), p <0.001. Conclusion: The incorporation of the main risk factors in ALL and the role of allo-HSCT into prognostic index for adults can adequately stratify the PFS of patients into 3 risk categories and could assist in clinical decision-making. Reference 1. Fernandes da Silva Junior W, Medina AB, Yamakawa PE, Buccheri V, Velloso EDRP, Rocha V. Treating Adult Acute Lymphoblastic Leukemia in Brazil-Increased Early Mortality Using a German Multicenter Acute Lymphoblastic Leukemia-based regimen. Clin Lymphoma Myeloma Leuk. 2018 Jun;18(6):e255-e259. doi: 10.1016/j.clml.2018.03.001. Epub 2018 Mar 14. PMID: 29605423. 2. Amir Enshaei , David O'Connor , Jack Bartram , Jeremy Hancock , Christine J. Harrison , Rachael Hough , Sujith Samarasinghe , Monique L. den Boer , Judith M. Boer , Hester A. de Groot-Kruseman , Hanne V. Marquart , Ulrika Noren-Nystrom , Kjeld Schmiegelow , Claire Schwab , Martin A. Horstmann , Gabriele Escherich , Mats Heyman , Rob Pieters , Ajay Vora , John Moppett, Anthony V. Moorman; A validated novel continuous prognostic index to deliver stratified medicine in pediatric acute lymphoblastic leukemia. Blood 2020; 135 (17): 1438-1446. doi: https://doi.org/10.1182/blood.2019003191