Reduced-intensity conditioning allogeneic transplant in heavily pre-treated chronic lymphocytic leukaemia patients: a single centre experience

Reduced intensity is preferred over myeloablative conditioning allogeneic HCT in chronic lymphocytic leukemia whenever indicated: A systematic review/meta-analysis

Despite availability of new and more effective therapies for chronic lymphocytic leukemia, presently this disease remains incurable unless eligible patients are offered an allogeneic hematopoietic cell transplant. Recent published clinical practice recommendations on behalf of the American Society for Blood and Marrow Transplantation relegated the role of for allogeneic hematopoietic cell transplantation to later stages of the disease. To our knowledge, no randomized controlled trial has been performed to date comparing myeloablative versus reduced intensity conditioning regimens in chronic lymphocytic leukemia patients eligible for the procedure. We performed a systematic review/meta-analysis to assess the efficacy of allogeneic hematopoietic cell transplantation when using myeloablative or reduced intensity conditioning regimens. We report the results in accordance to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Based on lower non-relapse mortality and slightly better overall survival rates, reduced intensity conditioning regimens appear to be the most desirable choice whenever the procedure is indicated for this disease. It appears highly unlikely that a RCT will be ever performed comparing reduced intensity vs. myeloablative allogeneic hematopoietic cell transplantation in chronic lymphocytic leukemia. In the absence of such a study, results of this systematic review/meta-analysis represent the best available evidence supporting this recommendation whenever indicated in patients with chronic lymphocytic leukemia.

Allogeneic transplantation for chronic lymphocytic leukemia

Even if Chronic lymphocytic leukemia (CLL) often has an indolent behavior with good responsiveness to cytoreductive treatment, about 20% of the patients, so called “poor-risk” patients, show an aggressive course and die within a few years despite early intensive therapies. Criteria for poor-risk disease according to the European Bone Marrow Transplantation (EBMT) CLL Transplant Consensus are: purine analogue refractoriness, early relapse after purine analogue combination therapy, CLL with p53 lesion requiring treatment.

Allogeneic transplant has potential curative role in CLL, however burden with very high transplant related mortality (TRM) rates of 38–50%. A major advance in reducing the short-term morbidity and mortality of allogeneic stem cell transplantation (SCT) has been the introduction of non-myeloablative or reduced intensity conditioning (RIC) regimens to allow engraftment of allogeneic stem cells. There is no doubt that the crucial therapeutic principle of allo-SCT in CLL is graft versus leukemia (GVL) activity.

The major complications of allogeneic SCT in CLL are: chronic graft-versus-host-disease (GVHD) affecting quality of life, high graft rejection and infection rates correlated with preexisting immunosuppression. Disease relapse remains the major cause of failure after RIC allo-HCT in CLL patients.

Sensitive minimal residual disease (MRD) quantification has strong prognostic impact after transplant.