Refractory Chronic Lymphocytic Leukemia: A Therapeutic Challenge

Despite impressive therapeutic progress represented by the advent of chemoimmunotherapy, chronic lymphocytic leukemia (CLL) remains incurable by conventional modalities. Refractory CLL defined by non-response to treatment or relapse/progression within 6 months is associated with multiple unfavourable prognostic factors such as p53 pathway disruption, deteriorating patient condition, increased risk of severe infections, and poor response to treatment, resulting in a very short overall survival. Therefore, refractory CLL represents a highly challenging situation for the hematologist as well as the patient. The amount and quality of data on refractory CLL are rather limited as clinical trials usually combine patients with relapsed and refractory disease. Therapeutic options for refractory CLL include alemtuzumab, ofatumumab, fludarabine- and bendamustine-based regimens, platinum-based aggressive protocols and high-dose corticosteroids combined with monoclonal antibodies. The recent introduction of ibrutinib and idelalisib, small molecules interfering with B-cell receptor pathways, revolutionized the treatment of refractory CLL by the novel concept of long-term, oral treatment leading to impressive progression-free and overall survival improvement. Allogeneic stem cell transplantation is still considered the only option with curative potential. This review focuses on the currently available therapeutic strategies for refractory CLL.