Long Term Follow up of Two Randomized Trials on Antithymocyte Globulin (ATG) for GVHD Prophylaxis in Unrelated Donor Transplants: Chronic GVHD, Bronchiolitis and Quality of Life.
Authors: Bacigalupo Andrea , Vignola Maurizio , Lamparelli Teresa , Bruzzi Paolo , Guidi Stefano , Alessandrino Paolo , Di Bartolomeo Palo , Oneto Rosa , Bruno Barbara , Barbanti Mario , Sacchi Nicoletta , Van Lint Maria Teresa , Bosi Alberto 
Published: April 2020

Background . We have reported that rabbit antithymocyte globulin (ATG Sangstat-Genzyme) prevents acute and chronic graft versus host disease (GvHD) in patients undergoing an unrelated donor transplant (Blood2001; 98 (10): 2942–2947). Patients had entered two consecutive randomized trials: in trial-1, 54 patients were randomized to non-ATG (n=25) or 7.5mg/kg rabbit ATG (n=29). In trial-2, 28 patients were randomized in the non-ATG arm and 27 in the ATG 15mg/kg arm.

Aim of the study: to assess the risk of extensive chronic GvHD, bronchiolitis obliterans , quality of life, survival and transplant related mortality (TRM) 4 years later.

Patients. Seventy five patients survived 100 days after BMT, and were available for analysis : in trial-1 there were 20 patients per arm, in trial-2 there were respectively 18 and 17 patients. The median follow up was 7.4 years for trial-1 and 5.3 years for trial-2. Each patients was updated and assessed for survival, chronic GvHD, for bronchiolitis , relapse of the original disease and quality of life.

Results. Results are given in percentage, in the order non-ATG vs ATG patients. At last follow up chronic GvHD (limited+extensive) was scored in 74% vs 33% respectively for non-ATG and ATG of patients in trial 1 (p=0.01) and in 61% vs 29% in trial-2 (p=0.06): when the two trials are combined cGvHD is scored in 68% vs 31% of non-ATG vs ATG patients (p=0.002). Extensive chronic GvHD was scored in both trials in 35% and 13% of patients (0.03). Bronchiolitis was present at last follow up in trial-1 in 50% vs 0% (p=0.01), and in 33% vs 8% in trial-2 (p=0.1). Combined data show bronchiolitis in 40% vs 4% of non-ATG vs ATG patients (p=0.002). Median timing of bronchiolitis was 1155 days. When patients developed bronchiolitis, the mortality was high (50%). Quality of life was assessed by looking at proportion of patients with Karnowski score of 100% at last follow up: the proportion was 37% vs 91% patients in trial-1 (p=0.02), it was 75% vs 100% patients in trial-2 (p=0.2) and overall in 56% vs 95% of all non-ATG vs ATG patiens (p=0.007). Relapse related deaths were 13% in the non-ATG and 11% in the ATG group. Survival: the actuarial survival at 5 years in trial-1 is 48% vs 53% (non-ATG vs ATG) and in trial-2 30% vs 41%. The actuarial TRM is 48% vs 40%, and in trial-2 it is 62% vs 47% (non-ATG vs ATG patients). Actuarial 5 year TRM in patients surviving one year (late TRM) is 28% vs 4% (p=0.02).

Conclusions. This updated analysis of two randomized GITMO trials, confirms with longer follow up, that ATG pre-transplant produces (1) a significant reduction of chronic GvHD (from 68% to 31%) and (2) a significant reduction of extensive chronic GvHD (from 35% to 13%). As a consequence quality of life is significantly improved in ATG patients. This study also shows that ATG reduces the risk of chronic bronchiolitis (from 40% to 4%), and late TRM (beyond one year) (from 28% to 4%). These data give strong support for the inclusion of ATG in the conditioning regimen of unrelated transplants: dosing and timing should be considered (Blood2003; 102 (11); 242a) and could be tested in a prospective trial. This work was supported by Fondazione CARIGE, GENOVA