Ibrutinib, Single Agent BTK Inhibitor, for Treatment Naïve (TN) and Relapsed/Refractory (R/R) Chronic Lymphocytic Leukemia: A Real-Life Experience from Rete Ematologica Pugliese (REP)

Background: Ibrutinib is a first-in-class oral inhibitor of Bruton Tyrosine Kinase (BTK) approved for the treatment patients with CLL who have received at least one prior therapy (R/R) or Treatment Naïve (TN) with del17p. Ibrutinib has been showed to improve progression free survival (PFS) and overall survival (OS) even in presence of del17p. Moreover there is a good tolerability profile such as to not lead to frequent and permanent interruption of therapy.Methods: In 131 CLL/SLL patients (including previously treated and untreated with del17) from eight different hematologic centers of REP (Rete Ematologica Pugliese) Ibrutinib 420 mg once daily was administrated until disease progression or unacceptable toxicity. PFS, OS and Overall response rate (ORR) were calculated. Kaplan Meier method was used to estimate PFS/OS and differences in survival times between groups were assessed with a log-rank test.Results: Among 131 pts, 9 (6.9%) received Ibrutinib as first line therapy (TN) and 122 (R/R) received prior therapies before Ibrutinib (39.7% BR, 18.3% FCR and other treatments); 90% (1-2) lines of therapy, 8% (3-4) lines and 2% more than 5. Median age of the 131 pts with CLL/SLL was 65 y (range, 28-84) with 50% ≥65 y.ECOG Performance Status was observed in 108 pts (0, 56%; 1, 40%; 2, 4%). FISH analysis was performed in 85/131 pts (65%) and some patients had more than one deletion. Among these, 42% had del17p (TN 100% and R/R 36%) and for the remaining R/R was 16% del13q, 4% del11q, 7% trisomy12 and in the others no abnormalities were found. Unmutated and mutated IGVH was performed in 78/131 patients (60%), 63% and 37% respectively. The ORR was 80% (complete response [CR], 10%) for all-treated pts (TN: 86%, R/R: 77%) and for R/R pts with del17p the ORR was 61%.With a median time on study of 17 months (range, 1-45), median PFS was not reached for all TN or R/R patients and the estimated PFS at 30 months was 66,7% for R/R patients. We exclude from our further analysis 9 TN patients because of the small sample size and the lack of events in a median follow up of 15 months (range, 3-24). In 122 R/R pts, median PFS was 39 months for pts with del17p and median PFS was not reached for pts without abnormality (overall logrank p=0.543). At 30 m the estimated PFS was 65.1% for del17p pts and 80.4% for no abnormality pts . Median OS was not reached for 122 R/R patients and the estimated PFS at 30 months was 72.7%. Median OS was not reached in pts with and without del17p (overall logrank p=0.807) with an estimated OS at 30 months of 81.7% and 90.2% respectively.In 47% of all treated patients adverse events (AEs) with grade ≥3 were neutropenia (16%), hypertension (12%), atrial fibrillation (3%), anemia (3%), diarrhea (2%). With a median follow up of 17 months 80% of pts remain on Ibrutinib treatment.Conclusions: In our real life experience with data from REP, Ibrutinib single agent demonstred to be effective. In R/R patients, with a median time on study of 17 months, the estimated PFS at 30 m was 66.7%. The differences in PFS between patients with and without del17p was not statistically significant (p=0.543) but at 30 months the estimated PFS was lower in del17p pts than in no abnormality pts (65.1% vs 80.4%).The treatment was well tolerated with AEs of grade ≥3 in a low percentage (36%) that did not result in treatment interruptions in the most of cases. Clearly, these results will require longer follow up time to be further confirmed.