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G. Del Poeta et al.
with >2 lines of therapy (Online Supplementary Figure S5). On the other hand, the clinical outcome was similar for patients receiving first-line ibrutinib and patients with one previous therapy, probably due to the high incidence of TP53 mutat- ed patients (24 of 26) in first-line setting (Online Supplementary Figure S5).
In CLL, the frequency of NOTCH1 M cases between 6- 12% if evaluated at presentation, increases to about 15- 20% in the context of fludarabine refractory patients.18,19 The higher frequency of NOTCH1 M characterizing our cohort of patients (36%) could be attributed both to the previous lines of chemotherapy and to the very low cut-off (>1%) chosen for NOTCH1 M. The adverse clinical out- come of patients with NOTCH1 M CLL was confirmed in univariate analysis in several independent cohorts of patients treated with chemo-immunotherapy.20-24 Since clon- al CLL cells accumulate because of prolonged survival due to impairment of apoptosis, the analysis of the BAX/BCL-2 ratio could be a valid tool to provide information on the chemo-sensitivity of CLL cells.9,10
We addressed the clinical impact of both NOTCH1 M, A
evaluated by NGS, and BAX/BCL-2 ratio, determined by flow cytometry, in patients with CLL homogeneously treat- ed with ibrutinib, mainly in a (R/R) setting. Determination of both parameters was done prior to starting ibrutinib ther- apy.
The NGS approach used for NOTCH1 M analysis allowed detection of allele frequency as low as 1%, high- lighting the presence of subclonal mutations in 32% of total NOTCH1 M cases.1,16,26 Of note, subclonal NOTCH1 M (i.e., VAF<10%) had similar prognostic impact as clonal muta- tions (Online Supplementary Figures S6 and S7); consistently a receiver operating characteristic curve analysis confirmed the use of 1% as optimal cut-off (Online Supplementary Figures S2). In this context, detection of NOTCH1 M by NGS could be viewed as a useful tool for clinical follow-up of patients as well as for minimal residual disease studies, although the latter use remains speculative at the moment. From a biological point of view, we found a significant rela- tionship between NOTCH1 and some other prognostica- tors. In particular, a significant correlation between NOTCH1 M and higher CD49d or CD38 expressions was
B
Figure 3. Progression-free survival and overall survival curves based on BAX/BCL-2 ratio within the subset of 113 patients from Rome. Kaplan-Meier plot compar- ing progression-free survival (PFS) (A) and overall survival (OS) (B) based on the BAX/BCL-2 ratio. Patients with a BAX/BCL-2 ratio <1.5 experienced both shorter PFS and OS.
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haematologica | 2021; 106(9)