Long-Term Evolution of Somatic Mutations in Patients with Del(5q) MDS Early Treated with Lenalidomide in the Sintra-Rev Clinical Trial: Safe and Effecitive Approach?

INTRODUCTION Lenalidomide (LEN) is the election treatment in del(5q) MDS, approved only in case of RBC transfusion dependency (TD). Only scarce retrospective data exploring LEN in non-TD setting are available, suggesting a benefit. SintraRev is the first randomized clinical trial evaluating LEN in del(5q) MDS with anemia but without TD. While efficacy has been confirmed in this trial, safety regarding clonal evolution and disease progression has not been addressed in this early treatment context. METHODOLOGY SintraRev is a phase III multicenter clinical trial in low-risk del(5q) MDS patients with anemia without TD. Patients were randomized (2:1) in a double-blind design to LEN (5mg/day continuously) vs placebo (PCB) for 2 years of treatment and 2 years of follow-up (FU). In addition to clinical results, we aimed to study the role of molecular profiling in this early therapeutic approach (LEN use prior to TD) in both arms during FU (baseline, week 12 and the last available FU). Next-generation sequencing (NGS) was performed in available samples. Sequential samples were collected before treatment initiation and then every 6 months until last FU. A capture-based NGS panel targeting 65 myeloid genes was used. Libraries were prepared following manufacturer's instructions (Twist BioScience) and run on Illumina sequencers. Mutations were considered at coverage of 2000x and >5% variant allele frequency (VAF). RESULTS Sixty-one patients were included in SintraRev with a median FU of 60.6 (32.3-73.9) months. A total of 47 patients (29 LEN, 18 PCB) had NGS data. At baseline, 32%, 36% and 32% of patients had 0, 1 and ≥2 mutations, respectively. More frequently mutated genes were SF3B1 (25.5% of patients) and TP53 (21%). No differences were observed regarding SF3B1 (p=0.74), TP53 (p=0.48) and DAT (DNMT3A, ASXL1 and TET2, p=1.0) mutations between groups. Furthermore, no differences in neither median number of mutations per patient (1: 0-4) nor VAF were found between LEN and PCB initially (p>0.05). At week 12, median VAF of mutations was significantly lower in the LEN group as compared to baseline (1.84% vs 9%, respectively p<0.01, n=21), but remaining stable in the PCB arm (18% w12 vs 17% baseline, p=0.594). Interestingly, in the long-term FU (median 22.4 months - 3.03 to 68.77) an increase in median VAF (from 17% to 29%, p<0.001, n=13) was observed in PCB arm (Fig 1). Clonal evolution among LEN & PCB patients during treatment was different, with a reduction in predominating clones in LEN arm, while remaining stable in the PCB group (Fig 2). In the long-term FU, both PCB & LEN showed acquisition of additional mutations (20% PCB & 22.7% LEN, p=1.0). Nevertheless, all these new mutations in the LEN group were acquired several months after loss of response to treatment or LEN discontinuation. Interestingly, dynamics of mutations under LEN treatment did not affect DAT mutations, which remained stable when cytogenetic response (CyR) was achieved. In this way, 87,5% of DAT mutations showed an independent behavior from the clone with 5q deletion. However, most SF3B1 (62,5%) and TP53 mutations (100%) were affected by LEN treatment in parallel with the disappearance of the del(5q) clone at the time of CyR. In this regard, responses were not affected by the persistence of DAT mutations (>80% of erythroid response, ER, and CyR) and interestingly, SF3B1mut patients achieved 100% of ER and CyR. In contrast, only 20% of TP53mut patients achieved ER and 60% CyR. AML evolution occurred in 13.8% and 22.2% patients in LEN & PCB arms, respectively (p=0.43). In patients transforming to AML, 50% had TP53mut in LEN while no TP53 mutations were found in PCB AML progression. No differences were found regarding median time to AML between the two groups (25.87 months, p=0.2). CONCLUSIONS MDS patients showing 5q deletion and without TD early treated with LEN did not showed more clonal evolution than the same set of patients in PCB arm. In fact, the acquisition of additional mutations in LEN patients was observed after loss of response or LEN discontinuation. Interestingly, molecular responses were confirmed in LEN patients by reduction of mutation's median VAF at week 12. Dynamic evolution of DAT alterations was not affected by LEN treatment, suggesting a role as CHIP-associated mutations. In contrast, most SF3B1 and TP53 mutations were modified in parallel with the del(5q) clone at the time of CyR. The maintenance of CHIP-related mutations did not affect either ER or CyR. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal