Adult Recipients of Matched Related Donor Blood Cell Transplants (BCT) Given Pretransplant Low-Dose Antithymocyte Globulin (ATG) Have Less Chronic Graft-Versus-Host Disease (cGVHD) and Transplant-Related Mortality (TRM): A Matched Pair Analysis.

Because pretransplant antithymocyte globulin (ATG) seems to reduce graft-versus-host disease (GVHD) and transplant-related mortality (TRM) after unrelated donor bone marrow transplant (BMT) we have investigated this agent in matched related donor (MRD) blood cell transplant (BCT). Of 82 adults receiving myeloablative conditioning and first MRD BCT between 01/99 and 05/02, 54 were matched for disease and stage with 54 patients (pts) not given ATG between 12/94 and 11/98. Median age was 42 (range 18 – 63) for ATG pts and 41 (range 22 – 54) for controls. Included in each group were 22 standard-risk pts (16 AML CR1, 6 ALL CR1), and 14 with high-risk acute leukemia of whom 12 had active AML (7 arising from MDS, 3 induction failures, 1 refractory, 1 relapse), and 2 ALL (1 refractory, 1 relapse). An additional 18 pts included 2 AML CR2, 1 ALL CR2, 2 CML AP/CP2, 2 MM, 8 relapsed/refractory NHL (2 mantle cell, 4 low, 1 intermediate, 1 high-grade) and 3 relapsed/refractory CLL. More control pts had conditioning incorporating TBI (32 vs 11, p<0.0001). All pts were given cyclosporine A and “short course” methotrexate with folinic acid. The study group received Thymoglobulin (Genzyme) (ATG) 4.5 mg/kg in divided doses over 3 consecutive days pretransplant finishing D0. ATG recipients were followed for 22 to 62 months (median 46) and control patients for 65–112 months (median 84). The actuarial incidence of acute GVHD grades II – IV was 25±6% in ATG recipients compared with 37±7% in the controls (p = ns). The figures for grade III – IV disease were 13±5% and 20±7% respectively (p = ns). Incidence of cGVHD at two years was 40±7% with ATG vs 97±3% without ATG (p < 0.0001), figures for extensive disease were 32±7% and 94±3% respectively (p < 0.0001). Sites of involvement by cGVHD were similar apart from gastrointestinal disease which was relatively more frequent in those ATG recipients who developed cGVHD (26% vs 5%, p = 0.03). Non-relapse mortality with and without ATG respectively was 4±3% vs 17±5% at 100 days and 9±4% vs 32±7% at 2 years (p = 0.004). Deaths were GVHD related in 3 ATG treated patients vs 13 controls (p=0.01). In the control group 2 year TRM was 26±8% in 32 TBI recipients compared with 42±11% in 22 patients not given TBI (p = ns). Relapse rate at 2 years was 36±7% for ATG recipients and 23±7% in controls (p = 0.06). Six of 21 relapsing patients in the ATG group survive having achieved another remission (4) or disease stabilization (2) after more treatment. One of 12 control patients who relapsed is currently alive in remission after a second BCT. Survival at 2 years was 70±6% in the patients given ATG vs. 54±7% in the controls (p=0.08) and progression-free survival was 57±7% vs 52±7% respectively. This study indicates that MRD BCT recipients given pretransplant ATG experience less cGVHD, less overall TRM and lower mortality related to both acute and chronic GVHD. These findings are not due to more control pts receiving TBI. Despite a trend to more relapse progression-free survival is unaffected, there is a trend to improved survival and presumably quality of life is generally better in ATG recipients because fewer of them have cGVHD.