Use of Thymoglobulin for Graft Versus Host Disease Prophylaxis Does Not Increase the Incidence of Clostridium Difficile Infection in Recipients of Allogeneic Stem Cell Transplant Recipients

Introduction: Clostridium difficile (C.diff) colitis (CDI) continues to be a common complication in recipients of allogeneic stem cell transplantation (AlloSCT). Multiple risk factors were associated with CDI in this patient population including prior CDI, antibiotic prophylaxis and therapy, acute graft versus host disease (aGVHD), etc. Our aim in this study was to evaluate the effect of thymoglobulin used in GVHD prophylaxis on the incidence of CDI in patients undergoing AlloSCT. Methods: We studied 3 consecutive cohorts of AlloSCT recipients. Group1- related donor AlloSCT without thymoglobulin (N=100, transplanted 3/2010-12/2013); group 2 - unrelated donor AlloSCT with thymoglobulin (N=110, transplanted 4/2012-12/2013); and group 3 - unrelated AlloSCT without thymoglobulin (N=100, transplanted 12/2009-12/2011). Majority of patients except three in group 3 were diagnosed with CDI with a PCR based test. Results: All 3 groups were similar with respect to the baseline characteristics (Table 1). The median follow up for the 3 groups was 2 years. At a median follow up of 2 years the incidence of CDI in the three groups were 19%, 26%, 28% respectively, p=0.2 (table 2). The incidence of CDI prior to aGVHD was similar in three groups (18/100, 25/110 and 19/100 in groups 1, 2 and 3 respectively). The incidence of CDI after development of aGVHD was higher in group 3 (1/100, 4/110 and 9/100 p=0.06 in groups 1, 2 and 3 respectively). The incidence of Grade II-IV aGVHD was significantly higher in group 3 (63%) as compared to groups 1 and 2 (49 and 41%) p=0.006 (Table 2). Similarly the incidence of any grade GI GVHD was higher in group 3 (44% Vs 23% and 24%) p=0.0009. The median time to development of aGVHD was similar in all three groups (28 days in groups 1, 31 days in group 2 and 26 days in group 2). Multivariable analysis revealed that none of the factors examined (age, sex, diagnosis, intensity of conditioning, type of transplant, use of thymoglobulin, acute GVHD) was related to development of CDI. Development of GI GVHD tended to increase the risk of subsequent CDI (40% vs 27%, p=0.06). Development of CDI did not increase the risk of development of subsequent GI GVHD (30% vs. 26%). Use of thymoglobulin improved two year overall survival in patients undergoing unrelated transplant (p=0.006). Conclusion: Thymoglobulin use did not affect the overall incidence of CDI in recipients of Allo-SCT. There is a trend towards increased incidence of late onset CDI in patients undergoing unrelated Allo-SCT and not recieving thymoglobulin probably because of higher incidence of GVHD and steroid use. There was no difference in the incidence of CDI in related vs. unrelated transplant recipients. Use of thymoglobulin improved survival in recipients of unrelated Allo-SCT. Disclosures Deol:Bristol meyer squibb: Research Funding. Lum:Karyopharm Therapeutics Inc: Equity Ownership; Transtarget.Inc: Equity Ownership. Revankar:Actelion, Merck, Gilead, Astellas: Research Funding; Dara biosciences: Consultancy. Chandrasekar:Merck, Glaxo, Chimerix,: Research Funding.