ALLOGENEIC HEMATOPOIETIC CELL TRANSPLANTATION IN THE TREATMENT OF CHRONIC LYMPHOCITIC LEUKEMIA : WHY AND WHEN ?

Chronic lymphocytic leukemia (CLL) is the most common hematologic malignancy in adults with an incidence rate of 4.2 per 100,000 per year. CLL frequently takes an indolent course, with some patients not requiring treatment for years, yet is incurable by currently available chemo- and immuno-therapeutic modalities. Despite high initial response rates, particularly to purine analogues, patients invariably relapse and subsequently develop resistance to therapy. The traditional “watchful waiting” approach to CLL is being challenged by data showing that treatments used early in the disease course impact long-term overall and progression-free survivals . The only curative treatment for CLL currently, is allogeneic hematopoeietic cell transplantation (alloHCT). In contrast to autologous transplant, myeloablative alloHCT for CLL patients generates durable remissions with promising survival plateaus; however, significant transplant related mortality (TRM) is also observed (25-50%) . At present the fact remains that for poor-risk CLL, alloHCT is the only treatment with the potential of providing long-term disease control. Future combinations with emerging low-toxicity therapies may further enhance the curative potential of allogeniec hematopoietic cell transplant. New drugs can also potentially enable refractory patients to attain response as a bridge to more effective stem cell transplantation