Reduced-Intensity Transplantation Feasible in Chronic Myeloid Leukemia

By Will Boggs, MD

NEW YORK NOV 25, 2005 (Reuters Health) - Hematopoietic stem cell transplantation after reduced-intensity conditioning (RIC) regimens is feasible in some patients with chronic myeloid leukemia (CML), according to a report in the November 1st issue of Blood.

"I think the registry data for reduced intensity allografts is encouraging and the transplant question now is "reduced intensity" or "conventional"," Dr. Charles Crawley from Addenbrookes Hospital, Cambridge, UK told Reuters Health.

Dr. Crawley and colleagues estimated the efficacy of RIC allografts in CML using data from the European Group for Blood and Marrow Transplantation (EBMT) on 186 patients from 33 centers.

Engraftment occurred in 94% of the patients, the authors report, regardless of the stem-cell source. The secondary graft failure rate was only 3%.

About half the patients developed acute graft-versus-host disease, the results indicate, and 42% of 137 evaluable patients went on to develop chronic GVHD.

Transplantation-related mortality was 3.8% at 100 days, 13.3% at one year, and 18.9% at two years, the researchers note. Transplantation-related mortality was lower among patients in chronic phase at the time of transplantation and lower when fludarabine/busulfan/anti-thymocyte globulin was used in the conditioning regimen.

Eighty-seven percent of the patients achieved remission by the time of first report, the investigators observe, and the cumulative probability of relapse at three years was 47%.

The three-year progression-free survival was 33%, and the probability of survival at three years was 54%. Overall survivals were higher for patients transplanted in chronic phase, first transplantations, and the use of fludarabine/busulfan/anti-thymocyte globulin, according to the results of a multivariate analysis.

The study "confirms the feasibility of RIC transplantation in CML and demonstrates efficacy particularly in chronic phase 1 or chronic phase 2," the authors conclude. "It also identifies good and poor risk factors and as such provides data for the rational design of the prospective studies that are now required."

"I don"t think we know which RIC regimen is best, and we don"t know whether T-depleting antibodies are a help or a hinder," Dr. Crawley said. "I tend to favor the fludarabine/busulfan regimens, but the evidence is weak."

"There remains a role for allogeneic transplant in CML despite the efficacy of imatinib, but the efficacy of transplant beyond chronic phase disease is poor," Dr. Crawley added. "It is important to identify patients whose response to imatinib is suboptimal so alternative strategies can be considered."

SOURCE:

• Blood 2005;106:2969-2976.