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

Relapsed/refractory chronic lymphocytic leukemia (CLL) represents a clinical challenge, in particular when high risk gene mutations occur. In this setting, alemtuzumab was recognized to be effective. This retrospective study evaluates long-term efficacy and tolerability of low-dose alemtuzumab in relapsed/refractory CLL and correlates clinical outcome with biological feature. Sixty-two consecutive patients (median age 68 years) were evaluated; alemtuzumab was administered 30 mg weekly for up to 18 weeks. Among the patients included in the analysis, 37% were fludarabine-refractory, 33.3% carried a TP53 disruption, 14.8% a NOTCH1 mutation and 9% a SF3B1 mutation. Overall response rate (ORR) was 61.3% (complete remission 25.8%). After a median follow-up of 43 months, overall survival (OS) and progression free survival (PFS) were 43.1 and 15 months, respectively; while ORR was 77.8% for patients carrying TP53 disruptions (OS 33.8 months) and 43.5% for fludarabine-refractory patients (OS 30 months). Noteworthy, long-term survivors (OS≥36 months) were 54.8%. None of the biological poor risk factors negatively impacted on ORR, PFS and OS. Grade ≥3 cytopenia occurred in 24.2% patients, 6.5% experienced a grade ≥3 non-CMV infection and no grade ≥3 CMV-event occurred. In conclusion, low dose-alemtuzumab is safe and effective in relapsed/refractory CLL, also in a long-term follow-up and high-risk genetic subgroups.