Retrospective review of relapse after allogeneic stem cell transplant for myeloid malignancy.

e18548 Background: Relapsed disease after allogeneic stem cell transplant (alloHSCT) is the leading cause of post-transplant death. We retrospectively characterized the outcomes of patients with relapsed myeloid malignancy after first alloHSCT between 2020-2022 at the Atrium Health Levine Cancer Institute and Wake Forest Baptist Health Comprehensive Cancer Center. We report outcomes based on pretransplant factors, graft versus host disease(GVHD) and post relapse management. Kaplan Meier Estimates were used to estimate median survival time with 95% confidence intervals and Cox Proportional Hazards models to estimate hazard rates. Methods: Overall, 58 patients were included. The median time to relapse was 188 days. 26 patients had myeloablative conditioning and 32 had reduced intensity. GVHD prophylaxis was PtCy in 35 patients, ATG/Tac/Mtx in 21 and Tac/Mtx in 2. 45 patients died at the time of analysis, with a median survival of 227 days after relapse. Patients with relapse prior to day +180 had median survival of 158 days while those who relapsed after day 180 had median survival of 292 days. 28 patients developed graft versus host disease (GVHD) before or after relapse. 5 patients received post-transplant maintenance therapy prior to relapse. 3 received gilteritinib, 1 decitabine and GCSF, and 1 oral azacitidine. After relapse, 26 patients were treated with hypomethylating agent (HMA) + venetoclax, 18 patients received HMA alone, 4 patients were enrolled on clinical trials and 15 patients received 2 or more lines of salvage therapy. 20 patients received DLI, with an average of 1.5 infusions (1-3). 4 patients developed GVHD after DLI. 3 patients received a second alloHSCT. Multivariable Cox Proportional Hazards models were made for time to relapse (TtR) and time to death following relapse (TtD). Results: For TtR, maintenance therapy was associated with a 94% decreased hazard ratio (HR) for relapse p=(0.001)[CI 0.01-0.31]. High risk cytogenetics had a 2.22 increased HR for relapse (p=0.086)[0.89-5.54]. For TtD, patients with GVHD prior to relapse had a marginally significant 57% lower HR for death (p=0.074)[0.17-1.09], while patients who developed GVHD after relapse had a 2.74 greater risk of death (p=0.123)[0.76-9.82]. Those who received DLI had a 90% reduced risk of death (p<0.001)[0.03-0.26]. Patients with HMA+venetoclax had a 2.31 times greater risk of death than patients on HMA alone (p=0.077). Conclusions: Patients with myeloid malignancies who experienced relapse after alloHSCT had poor prognosis. Development of GVHD prior to relapse trended toward improved survival after relapse. In this cohort, maintenance chemotherapy prior increased time to relapse and DLI improved survival after relapse. The addition of venetoclax to HMA was associated with poorer survival compared to HMA alone. Patient characteristics. Gender M/F 33/25 Age <=65/>65 26/22 Disease AML 38 MDS 17 MDS/MPN 2 CMML 1 Donor Source MRD 7 MUD 34 Haplo 15 mMRD 1 mMUD 1