A Matched Pair Retrospective Comparison of Adult Unrelated and Sibling Donor Allogeneic Transplantation for AML.

Aim: Recent studies have shown equivalent survival outcomes for unrelated donor transplants for CML compared to siblings. This study compares outcomes for a set of unrelated donor transplants for AML and a strictly selected matching set of sibling donor transplants.

Method: A set of 100 adult first 6/6 compatible unrelated donor transplant recipients with AML were selected from the ABMTRR database. A set of 100 adult first 6/6 compatible sibling donor controls were selected, matched with the subjects on disease stage, sex and age. Additional data was collected from participating centres on conditioning, prophylaxes, GVHD and other outcome factors.

Results: A total of 162 forms were returned: 22 for good risk (CR1 - 15 siblings, 7 unrelated) and 140 for poor risk (past CR1 - 77 siblings, 63 unrelated). A Kaplan-Meier comparison of post transplant disease free survival between good risk sibling and unrelated donor recipients was not statistically significant (p=0.2). However the 5-year DFS of poor risk unrelated recipients was significantly worse than sibling recipients (sibling 29.5%, unrelated 14.1%, p=0.01). In a multivariate Cox regression model, the independent risk factors for DFS among all patients were unrelated donor (p=0.003), disease stage beyond CR1 (p=0.04), recipient male (p=0.04), aged 40 and over (p=0.04) and CMV positive (p=0.03).

Conclusion: Adult unrelated donor allograft recipients in poor risk AML have poorer DFS probability than sibling recipients. However in good risk AML allograft recipients, donor type is not a significant DFS risk factor. The ABMTRR is an important national data resource providing a large and readily accessible sample frame for retrospective studies on specific transplant indications.