Considering Bone Marrow Blasts from Nonerythroid Cells Improves the Prognostic Evaluation of Myelodysplastic Syndromes with Ring Sideroblasts

Introduction: As showed in a recent study of our group, considering bone marrow (BM) blasts from nonerythroid cellularity (NECs) improves the prognostic evaluation of MDS (Arenillas et al, J Clin Oncol 2016). By enumerating blasts from NECs, 12% of MDS patients diagnosed within WHO categories with less than 5% BM blasts were reclassified into higher-risk categories and showed a poorer overall survival than did those who remained in the initial categories. Refractory anemia with ring sideroblasts (RARS) and refractory cytopenia with multilineage dysplasia and ring sideroblasts (RCMD-RS) have shown an special good outcome in different studies. As MDS with ring sideroblasts (MDS-RS) usually present a high percentage of BM erythroblasts, considering BM blasts from NECs could imply a risk overestimation of this subset of patients.

Aim: we evaluated the relevance of considering BM blasts from NECs or from total nucleated cells (TNCs) on classification and prognostication of the group of patients diagnosed with MDS-RS.

Methods: We retrospectively analyzed 3,924 de novo MDS diagnosed according to WHO 2001 and 2008 classifications from the MDS Spanish registry. 1,045 patients presented less than 5% BM blasts from TNCs and equal or greater than 15% BM ring sideroblasts, fulfilling current definition for RARS (WHO 2001 and 2008) and RCMD-RS (WHO 2001). Moreover 1,233 patients with equal or greater than 5% BM ring sideroblasts and less than 5% BM blasts were analyzed in order to explore the future definition of WHO 2016, that considered as MDS-RS those patients with 5%-<15% BM ring sideroblasts if SF3B1 mutation is present. This was a tentative analysis since SF3B1 mutation information was not available in our series. Percentage of BM blasts from NECs was calculated as follows: [%BM blasts from TNCs/(100 - %BM erythroblasts) x 100]. Survival curves were constructed by using the Kaplan-Meier method and compared using the log-rank test. Univariable and multivariable Cox regression analysis were also implemented.

Results: Median age at diagnosis of MDS-RS was 76y (25-101) and 59% were males. Estimated median follow-up, as calculated by reverse Kaplan-Meier method, was 50.1 months (95% CI, 45.5-54.7) and median OS was 96.5 months. By enumerating blasts from NECs, 10% of MDS-RS patients were reclassified into categories with equal or greater than 5% BM blasts and showed a poorer overall survival (OS) than did those who remained in initial categories (median OS, 68.1 vs 97.6 months, P=0.025; Hazard ratio (HR): 1.41; 95%CI: 1.04-1.91; p=0.026). After adjusting the survival analysis by IPSS cytogenetic risk groups, the prognostic impact of BM blasts considered from NECs maintained its significance (HR: 1.37; 95%CI: 1.01-1.85; p=0.045). Similar results were observed applying this method to the group of MDS patients with equal or greater than 5% BM ring sideroblasts and less than 5% BM blasts. By considering blasts from NECs, 10% of this subset of patients were reclassified into categories with equal or greater than 5% BM blasts and showed a poorer OS than did those who remained in initial categories (median OS, 60.2 vs 85.8 months, P=0.003; HR: 1.51; 95%CI: 1.15-1.97; p=0.003; HR adjusted for IPSS cytogenetics: 1.46; 95%CI: 1.12-1.92; p=0.006).

Conclusion: considering bone marrow blasts from nonerythroid cells improves the prognostic evaluation of MDS with ring sideroblasts.

Written on behalf of the Grupo Español de Síndromes Mielodisplasicos (GESMD).