Relative Impact of NOTCH1/SF3B1 Mutations, Complex Karyotype and TP53 Disruption in the Prognosis of Chronic Lymphocytic Leukemia Patients.

Whole genome and exome sequencing studies recently revealed that CLL genome harbors frequent recurrent mutations as NOTCH1, TP53 and SF3B1 genes. Mutational status of these three genes strongly impacted on treatment-free survival (TFS) and overall survival (OS) in pioneer reports. In this retrospective series, we evaluated the relative role of these mutations along with the karyotype in untreated CLL patients, and after immunochemotherapy given first-line.

164 patients were included (all naïve from chemotherapy), including 108 who further necessitated therapy according to NCI2008 guidelines. Mutational studies (IgVH sequence, NOTCH1, SF3B1, and TP53 genes) were available in 164/164, FISH (del17p and 11q) in 156/164, and conventional karyotype in 140/164. TFS and OS were calculated from diagnosis and first-line treatment or death respectively, progression-free survival (PFS) was calculated in 108 patients who received rituximab-based immunochemotherapy frontline (94 FCR, 14 R-alkylators), from end of therapy to relapse (according to NCI2008 definition). In 60/94 patients, minimal residual disease (MRD) was assessed three months after completion of FCR by 4-color flow cytometry, according to published guidelines for MRD monitoring.

Thirty-seven patients (22.6%) have at least one somatic mutation (TP53, SF3B1 or NOTCH1 genes), 22 NOTCH1 mutations (13.4%), 10 SF3B1 mutations (6.1%) and 8 TP53 mutations (4.5%). SF3B1 mutations are located mainly on the exon 14. TP53 mutations are located mainly on the exon 8 (4/9) and double mutation of TP53 was not detected. Three patients had a mutation of NOTCH1 or SF3B1 combined to a TP53 mutation. Conventional karyotype was obtained in 135/140 CLL (96.4%, 5 culture failures) and 116/135 (85.9%) were associated with chromosomal aberrations. Complex karyotype (CK) and balanced translocations involving IgH locus were shown in 23.9% and 8.1% of patients, respectively. NOTCH1 mutations were found significantly associated with unmutated IgVH and trisomy 12, SF3B1 mutations with male gender and advanced Binet stage, both somatic mutations being mutually exclusive. As expected, TP53 mutations associated with del17p.

After a median follow-up of 5 years, 108/164 patients had received frontline immunochemotherapy, for a median treatment-free survival (TFS) of 41.6 months from diagnosis of CLL. Only 8/164 had died, for a median overall survival (OS) not reached, but a 10y probability of survival of 92%. On univariate analysis, shorter TFS was correlated with age<65y, del11q, mutation of SF3B1, CK, IgVH unmutated, and Binet stage (B versus A), only the two latter remaining significant on multivariate analysis. Shorter OS was correlated to male sex, mutation of SF3B1, CK, and dysfunctional TP53 pathway (by mutation and/or deletion), only the three latter remaining significant on multivariate analysis.

A total of 108 patients received immunochemotherapy first-line (FCR in 94 patients, and rituximab-alkylating agent in 14 patients (R-CHOP, R-CVP, R-CD, R-bendamustine). Frequencies of NOTCH1 and SF3B1 mutations, and of CK were 17.7%, 8% and 32.2% respectively. On multivariate analysis, variables associated with PFS (older age, TP53 disruption, and MRD level 3 months after completion of FCR), time-to-next-treatment and OS (CK and TP53 disruption) further demonstrated that TP53 deletion/mutation and conventional karyotyping should be prospectively assessed before initiation of FCR. Of note, our data also suggested that FCR could have overcome the previously reported prognostic impact of NOTCH1 and SF3B1 mutations.

Despite similar frequencies and distributions among defined prognostic groups (Binet, IgVH, FISH), NOTCH1 mutations were not associated with reduced TFS or OS in CLL patients naive from treatment, whereas SF3B1 mutations correlated with OS. In the 108 patients receiving immunochemotherapy, TP53 disruption and complex karyotype were independently and significantly linked to OS. This study is the first to suggest that FCR therapy may overcome the reported adverse prognosis endowed with NOTCH1 mutations.

No relevant conflicts of interest to declare.