Predictors of Disease Progression and Survival in Patients with Myelodysplastic Syndrome Secondary to Inherited Bone Marrow Failure Syndromes

Introduction Inherited bone marrow failure syndromes (IBMFSs) are rare genetic disorders characterized by abnormal hematopoiesis resulting in cytopenias, risk of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Once patients develop MDS, the only cure is hematopoietic stem cell transplant (HSCT). Proceeding to HSCT before transformation to advanced MDS or AML leads to better outcomes (Smith et al., PBC 2013). The rate of disease progression from early MDS to advanced MDS or AML is variable and risk factors for progression in IBMFS patients are unknown. We hypothesized that certain variables could predict the likelihood of progression, and that the type of disease progression may impact overall survival (OS).

Methods Data were collected from patients prospectively enrolled in the Canadian Inherited Marrow Failure Registry (CIMFR), a Canadian collaboration including >95% of pediatric IBMFS patients. Patients were diagnosed with a specific syndrome or unclassified IBMFS (ucIBMFS) based on published criteria. Diagnostic criteria for pediatric MDS defined by Cada et al. (Haematologica 2015) were used, patients with refractory cytopenia (RC) with or without dysplasia or ringed sideroblasts were included. Patients with refractory cytopenia with excess blasts (RCEB) were excluded. MDS progression was defined as 1 or more of: a new cytogenetic abnormality, more advanced cytopathology, worse cytopenias requiring HSCT. Variables evaluated included: involvement of specific organ systems, hematologic parameters within 3 months of cytogenetic clones/MDS diagnosis, type of mutation (as per Waespe et al., Genomic Medicine 2017). Univariate Cox Proportional Hazard modelling was used to estimate association with specific variables and disease progression, Kaplan-Meier analysis was used for survival evaluation.

Results Between January 1, 2001 and November 30, 2018, 601 patients were enrolled in the CIMFR, and during this time 59 (9.8%) developed cytogenetic clones/MDS. Four did not meet the pre-defined criteria for IBMFS, 9 had RCEB at diagnosis with MDS and 1 did not have data available; these were excluded from our cohort of 45 patients.

Twelve (26%) patients with clones/MDS had Fanconi Anemia (FA), 13 (28.3%) had Shwachman-Diamond Syndrome (SDS), 5 (10.8%) had ucIBMFS, 15 (33.3%) had other IBMFSs. The most common cytogenetic finding at diagnosis was -7/-7q (n=10, 22%). Patients who developed clones/MDS had significantly worse OS compared to those without clones/MDS (HR 3, 95% CI 2-6, p<0.0001). Among patients who developed clones/MDS, 22 (48.9%) underwent HSCT.

Twenty one clones/MDS patients (46.7%) had disease progression, with a median time to progression of 7.9 months (1.2-131.4). The majority (68.4%) developed progression within one year of clones/MDS diagnosis. Nine (42.8%) developed more advanced cytopathology, 9 (42.8%) a new cytogenetic abnormality and 5 (23.8%) worsening cytopenias. Most patients with FA (67%) had disease progression, compared to 38.5% of patients with SDS. Mutation types (classified as more vs less deleterious) were similar between the groups with and without progression.

The evaluated hematologic parameters (MCV, hemoglobin, platelets and neutrophils within 3 months of diagnosis) were not predictive of disease progression. Patients with disease progression, when compared to those without, were more likely to have congenital malformations of the skin (14.3% vs 0%), cardiovascular system (28.6% vs 4.2%) and kidneys (14.3% vs 4.2%). No specific system involvement predicted disease progression, although congenital malformations of the cardiovascular system had a HR of 2.63 (95% CI 0.93-7.42).

Conclusion Development of MDS has a significant adverse impact on the OS of IBMFS patients, with disease progression typically occurring within the first year after MDS diagnosis. Patients with FA have a high risk of disease progression. Hematologic parameters were not predictive of the risk of disease progression, however, the presence of congenital cardiovascular anomalies is suggestive of increased risk of disease progression and warrants further investigation. Our study is limited by the rare nature of IBMFSs and MDS and the collection of additional data will help to guide treatment decisions for this high-risk patient population.

Acknowledgment The authors thank Mr. Bryan Maguire for his statistical analysis of data related to this work.

Klaassen:Takeda: Consultancy; Sanofi: Consultancy; Octapharma AG: Consultancy; Novo Nordisk: Consultancy; Hoffman-La Roche: Consultancy; Cangene: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Agios Pharmacueticals: Consultancy; Principia Biopharma: Patents & Royalties; Novartis: Research Funding.