CD49d Expression Is Included in a Revised 4-Factor Model Predicting Outcome in Patients with Chronic Lymphocytic Leukemia Treated with Ibrutinib: A Multi-Center Real-World Experience

Introduction. Expression of the CD49d integrin chain has prognostic impact on ibrutinib (IB)-treated CLL patients (Tissino et al, J Exp Med, 2018; Tissino et al, Blood 2020). In addition, a 4-factor (4-f) score, based on TP53 aberration, β2-microglobulin (β2M), lactate dehydrogenase (LDH) and previous therapy lines was proposed to identify patients at a higher risk of treatment failure or death during IB therapy (Ahn et al, J Clin Oncol, 2020; Morabito et al, Am J Hematol, 2021). The clinical impact of TP53 disruption was recently refined by demonstrating that only the co-presence of TP53 deletion and mutations, and not the single aberrations, has prognostic value in the IB setting (Bomben et al, Leukemia 2022). The aim here is to integrate these observations in a comprehensive scoring for the management of IB-treated patients. Methods. This study is a retrospective/multicenter analysis of 410 CLL patients treated with IB in the current clinical practice (December/2013-March/2021). Outcome data were updated as of March/2023. Median follow-up from IB treatment was 29.5 months (95% CI 26.7-33.1 months); 57 patients were treatment naïve (0 previous lines), while 353 had ≥1 previous lines. CLL patients were characterized for CD49d expression and for the 4-f variables, TP53 disruption was evaluated by FISH and TP53 mutational status by NGS (low-VAF mutations included). OS or PFS were measured from the date of IB treatment to the date of death (OS), or progression/death (PFS) or last follow-up. Results. 1) The canonical 4-f was applied as previously described, identifying 111 low-, 163 intermediate (int)-, and 136 high-risk patients. Patients in the low-risk group had a longer OS than patients in the int-, and high-risk groups ( P=0.0115 and P=0.0011), while no difference was found comparing patients in the int- vs. high-risk groups (P=0.3036). 2) We generated a modified version of the 4-f score by considering: i) as TP53 disrupted only patients presenting a concomitant TP53 deletion and mutation (n=93); ii) since no difference in terms of OS was found comparing previously untreated patients (n=57) and patients treated with 1 previous line (n=157; P=0.78), these two groups were combined (n=214) and kept separated from patients who had received >1 previous lines of therapy (n=196). Accordingly, the 4-f-modified identified 218 low-, 109 int-, and 83 high-risk patients, the 3 groups presented different OS, the latter model outperforming the canonical 4-f score (C-i