Mutations of NOTCH1 Are An Independent Predictor of Survival in Chronic Lymphocytic Leukemia

Abstract

283 The clinical course of chronic lymphocytic leukemia (CLL) ranges from very indolent, with a nearly normal life expectancy, to rapidly progressive leading to death and occasionally undergoing transformation to Richter syndrome (RS). TP53 disruption identifies a fraction of high risk CLL destined to experience a very short survival. High risk CLL, however, cannot be fully recapitulated by TP53 disruption and other lesions of cancer genes may be implicated in this aggressive phenotype. Analysis of the CLL coding genome has recently disclosed that the NOTCH1 proto-oncogene is recurrently mutated at CLL presentation. Here we assessed the prognostic role of NOTCH1 mutations in CLL. Two series of previously untreated CLL were utilized as training (n=309, median follow-up 6 years) and validation (n=230, median follow-up 7 years) cohorts. NOTCH1 mutations were analyzed by DNA Sanger sequencing in blind with respect to clinical data. In the training series, NOTCH1 mutations occurred in 34/309 (11.0%) patients, being mostly represented (26/34, 76.5%) by a recurrent two bp frameshift deletion (c.7544_7545delCT). The remaining NOTCH1 mutations (8/34, 23.5%) were frameshift deletions other than c.7544_7545delCT (n=7) and frameshift insertions (n=1). All mutations were predicted to disrupt the NOTCH1 PEST domain. CLL with NOTCH1 mutations preferentially carried unmutated IGHV genes (76.5%, p<.001). Other characteristics at presentation associated with NOTCH1 mutations were advanced Rai stage (26.5%, p=.006) and trisomy 12 (44.1%, p<.001). By univariate analysis, NOTCH1 mutations associated with an increase in the hazard of death (HR: 3.77; 95% CI: 2.14–6.66) and a significant overall survival OS shortening (p<.001) (Fig. 1A). Multivariate analysis selected NOTCH1 mutations as an independent risk factor of OS (HR: 4.22; 95% CI: 2.15–8.28; p<.001), after adjusting for age (p<.001), Rai stage (p=.005), IGHV mutation status (p=.465), 11q22-q23 deletion (p=.128), trisomy 12 (p=.183) and TP53 disruption (p<.001). The poor prognosis conferred by NOTCH1 mutations was attributable, at least in part, to a shorter time to progression requiring treatment (p<.001), and a higher cumulative probability of RS development (p=.026). Although NOTCH1 mutated patients were devoid of TP53 disruption in 31/34 (91.2%) cases, the OS predicted by NOTCH1 mutations was similar to that of TP53 mutated/deleted CLL (Fig. 1C). Analysis of the validation series confirmed: i) the prevalence of NOTCH1 mutations at CLL presentation (26/230, 11.3%); ii) the spectrum of NOTCH1 mutations at CLL presentation (c.7544_7545delCT: 21/26, 80.7%; other mutations: 5/26, 19.3%) iii) the adverse prognostic impact of NOTCH1 mutations in CLL both by univariate analysis (Fig. 1B) and by multivariate analysis (HR: 2.08; 95% CI: 1.10–3.93; p=.023); iv) the preferential mutually exclusive distribution of NOTCH1 mutations and TP53 disruption (25/26, 96.2%); v) that OS of NOTCH1 mutated CLL is similarly poor as that of TP53 disrupted CLL (Fig. 1D). The current study on 539 CLL documents that NOTCH1 mutations: i) represent one of the most frequent cancer gene mutations known to be involved at CLL presentation; ii) identify a subgroup of patients showing poor OS similar to that of TP53 disrupted cases; iii) exert a prognostic role independent of widely accepted clinical and genetic risk factors; iv) predict OS in series from different institutions, as documented by the training-validation approach chosen for the design of this study. Disclosures: No relevant conflicts of interest to declare.

Distinct immunoglobulin heavy chain variable region gene repertoire and lower frequency of del(11q) in Taiwanese patients with chronic lymphocytic leukaemia

“…It is plausible that different times of sample collection from untreated patients was one of the major reasons to explain these discrepancies. The relationship among molecular alterations in our study was mostly consistent with the reported data, including that NOTCH1 mutations occurred exclusively without TP53 mutations (Rossi et al , ) and un‐mutated IGHV was frequently associated with SF3B1 mutations (Xia et al , ). However, more IGHV ‐mutated patients in our cohort had ZAP70 expression compared with that of reported data (Wiestner et al , ).…”

Stereotyped subset #1 chronic lymphocytic leukemia: a direct link between B‐cell receptor structure, function, and patients' prognosis

“…We do not confirm the reported specific association of subset #1 with del(17p) , although this aberration was present in almost one‐third of cases. The evaluation of the recently identified gene mutations did not show a specific enrichment in NOTCH1 (15%) or BIRC3 mutations (5%) among subset #1 CLL, who presented a prevalence similar to what reported among UM CLL at diagnosis . No SF3B1 mutation was identified.…”

“…All mutations identified in WGA were confirmed using the corresponding gDNA. PCR primers and conditions have been previously described . As BIRC3 might be affected also by deletions, FISH analysis using the RP11‐177O8 probe was performed, as described .…”

Low‐dose alemtuzumab in refractory/relapsed chronic lymphocytic leukemia: Genetic profile and long‐term outcome from a single center experience

“…Relapsed/refractory CLL patients consecutively treated with alemtuzumab between 2003 and 2013 were identified in the institutional database, and baseline clinical data, treatment modalities, efficacy, safety and disease course were extracted. Tumor samples collected before treatment start were assessed for FISH karyotyping, expression of ZAP‐70, CD38, and CD49d, mutational status of the IGHV, TP53, NOTCH1, SF3B1, and BIRC3 genes .…”