Among patients with refractory anemia with ring sideroblasts, the presence of a common mutation in SF3B1 appears to be a marker for an indolent clinical course and favorable outcome compared to patients with wild-type SF3B1, European investigators reported.

The gene SF3B1, which encodes for a splicing factor subunit, is frequently mutated in cases of chronic lymphocytic leukemia and myelodysplastic syndromes.

“SF3B1 mutation is a major determinant of disease phenotype and clinical outcome in MDS [myelodysplastic syndrome] with ring sideroblasts. SF3B1-mutated MDS is characterized by homogeneous hematologic features, favorable prognosis, and restricted patterns of co-mutated genes and clonal evolution. Overall, these results strongly support the recognition of MDS associated with SF3B1 mutation as a distinct MDS subtype. Conversely, SF3B1-negative MDS with ring sideroblasts represents a subset with a high prevalence of TP53 mutations and worse outcome that should be taken into consideration in clinical decision-making,” the study authors conclude.

Dr. Luca Malcovati and his colleagues from the University of Pavia, Italy, and other European centers, conducted a mutational analysis of 293 patients with myeloid neoplasms and 1% or more ring sideroblasts. They found somatic mutations in SF3B1 in 129 of 159 patients with refractory anemia with ring sideroblasts (RARS) or refractory cytopenia with multilineage dysplasia and ring sideroblasts (RCMD-RS). In contrast, there was a significantly lower prevalence of SF3B1 mutations among 50 patients with myelodysplastic/myeloproliferative neoplasm (MDS/MPN), and among 84 additional patients with other myeloid diseases under the World Health Organization classification of disorders of hematopoietic and lymphoid tissues (P < .001).

In multivariable analyses controlling for demographic and disease-related factors, patients with SF3B1 mutations had significantly better overall survival (hazard ratio, 0.37; P = .003), as well as a lower cumulative incidence of disease progression (HR, 0.31; P = .018), compared with patients with wild-type SF3B1 ( Blood 2015;126[2]:233-41 ).

Mutations in SF3B1 were predictive of better outcomes among patients with RARS, RCMD-RS, and in patients with MDS without excess blasts.

When they looked at other mutations, the investigators found that in patients with SF3B1 mutations, the mutations in DNA methylation genes were associated with the presence of multilineage dysplasia, but this association had no significant effect on clinical outcomes.

Among patients with wild-type SB3B1, mutations in TP53 were frequently seen, and these mutations were associated with poor outcomes.