Validation of the EBMT risk score in chronic myeloid leukemia in Brazil and allogeneic transplant outcome

Abstract

Background and objectives: The management of chronic myeloid leukemia (CML) has changed radically since the introduction of imatinib therapy. The decision of whether to offer a patient a hematopoietic stem cell transplant (HSCT) must be based on the probability of success of the procedure. The aim of this retrospective analysis of 1,084 CML patients who received an allogeneic HSCT in 10 Brazilian Centers between February 1983 and March 2003 was to validate the EBMT risk score.

Design and methods: The study population comprised 647 (60%) males and 437 (40%) females, with a median age of 32 years old (range 1 - 59); 898 (83%) were in chronic phase, 146 (13%) were in accelerated phase and 40 (4%) were in blast crisis; 151 (14%) were younger than 20 years old, 620 (57%) were between 20 and 40 and 313 (29%) were older than 40; 1,025 (94%) received an HLA fully matched sibling transplant and only 59 (6%) received an unrelated transplant. In 283 cases (26%) a male recipient received a graft from a female donor. The interval from diagnosis to transplantation was less than 12 months in 223 (21%) cases and greater in 861 (79%). The overall survival, disease-free survival, transplant-related mortality and relapse incidence were 49%, 50%, 45% and 25%, respectively.

Results: Of the 1084 patients, 179 (17%) had a risk score of 0 or 1, 397 (37%) had a score of 2, 345 (32%) had a score of 3, 135 (12%) had a score of 4 and 28 (2%) a score of 5 or 6. The overall survival (OS) rate in patients with risk scores 0-1 and 2 was similar (58% and 55%, respectively) but significantly better than that in patients with scores 3 or more (score 3 - 44%, 4 - 36 % and 5-6 - 27%, respectively) pp<0.001). Disease-free survival (DFS) and transplant related mortality (TRM) in a patients with a score of 3 or more were 46% and 49%, respectively and the relapse rate beyond score 5-6 was 77%. Disease status had a negative impact on all outcomes (OS, DFS, TRM, and relapse). The OS rate for male recipients of a graft from a female donor was 40% compared to 52% among the other donor-recipient pairs (p=0.004). DFS and TRM were significant for disease phase and female donor-male recipient (p<0.001 and p<0.003, respectively). In our experience, age and interval between diagnosis and transplant did influence OS, DFS, TRM, and relapse rate.

Interpretation and conclusions: Our results validate the EBMT risk score in the context of a developing country and confirm its usefulness for making point decisions in the imatinib era.