An analysis comparing reduced-intensity conditioning and myeloablative therapy for CLL

This study analyzed the results of 37 studies comparing myeloablative therapy and reduced intensity conditioning (RIC) before stem cell transplantation in patients with chronic lymphocytic leukemia (CLL). This study concluded that RIC was associated with lower mortality and better survival compared to myeloablative therapy.

Allogeneic stem cell transplantation (allo-SCT) after chemotherapy is a curative treatment option for CLL. This is when blood-forming cells destroyed by chemotherapy are replaced with stem cells (immature cells) from the blood or bone marrow of a donor. When high-doses of chemotherapy are delivered before a stem cell transplant, this is called myeloablative therapy. However, not all patients can tolerate conventional myeloablative conditioning. Older patients or those with additional medical conditions are particularly likely to experience serious side effects. These patients may receive reduced-intensity conditioning (RIC). This is designed to suppress the patient's immune system enough so that it will accept the donor stem cells. Once the donor's cells take over the patient's bone marrow (a process known as engraftment), the immune system is better able to kill cancer cells.

This study aimed to compare myeloablative therapy and RIC techniques in CLL patients. The results of 37 separate studies were pooled into a single analysis. All studies compared treatment outcomes between myeloablative therapy and RIC. Most studies included analyzed the records of patients already treated. Four studies randomly assigned patients to treatment groups. Study follow-up ranged from 12.6 to 138 months.

The pooled complete response (no sign of active disease) rate for myeloablative therapy was 58%. Pooled overall survival (time from treatment until death from any cause) was 51%. Mortality rate without a documented relapse was 32%. 41% of patients treated with myeloablative therapy showed no signs of progression during the study period. Chronic graft-versus-host disease (when donor cells attack the organs of the patient) was observed in 59% of patients.

The pooled complete response rate for RIC was 63%. Pooled overall survival was 60%. Mortality rate without a documented relapse was 23%. 47% of patients treated with RIC showed no signs of progression during the study period. Chronic graft-versus-host disease was observed in 53% of patients.

4 studies randomly assigned patients to treatment groups. The pooled complete response rate for RIC in these studies was 74%. Overall survival was 62%. Mortality rate without a documented relapse was 24%. 43% of patients randomly assigned to RIC showed no signs of progression during the study period. Chronic graft-versus-host disease was observed in 75% of patients. 

Authors concluded that RIC showed overall better outcomes compared to myeloablative therapy for CLL patients undergoing allo-SCT.