Background: Patients with high-risk acute leukemia have a high risk of relapse after allogeneic stem cell transplantation (allo-SCT). In an effort to reduce the relapse rate, various therapeutic methods have been implemented into clinical practice. Among them, prophylactic donor lymphocyte infusion (pro-DLI) has shown significant efficacy. However, the widespread application of pro-DLI has been restricted mostly due to concerns regarding the development of graft versus host disease (GVHD). In the present study, we tested the safety and efficacy of a novel method of prophylactic-DLI based by repetitive administration of low lymphocyte doses. Methods: DLI was administered to patients with high-risk acute leukemia at a dose of 2 × 10⁶/kg CD3-positive cells. DLI at the same dose was repeated every two months for at least 36 months post-allo-SCT, or until relapse or any clinical or laboratory feature suggested GVHD, whichever occurred first. Forty-four patients with a median age of 53 years (range 20–67) who underwent allo-SCT between 2011 and 2020 were included in our study. Thirty-three patients with high-risk acute myeloid leukemia (AML) and 11 with high-risk acute lymphoblastic leukemia (ALL) after allo-SCT from a matched sibling (MSD, no = 38 pts) or a matched-unrelated donor (MUD, no = 6 pts) received pro-DLI. Twenty-three patients were in CR1, all with unfavorable genetic features; 12 patients were in CR2 or beyond; and 9 patients had refractory disease at the time of transplant. Ten out of 23 patients in CR1 had detectable minimal residual disease (MRD) at the time of allo-SCT. Disease risk index (DRI) was high and intermediate in 21 and 23 patients, respectively. Conditioning was myeloablative (MAC) in 36 and reduced intensity (RIC) in 8 patients, while GVHD prophylaxis consisted of cyclosporine-A in combination with low-dose alemtuzumab in 39 patients or with low-dose MTX in 5 patients, respectively. Results: Thirty-five patients completed the scheduled treatment and received a median of 8 DLI doses (range 1–35). Fifteen out of 35 patients received all planned doses, while DLI was discontinued in 20 patients. Reasons for discontinuation included GVHD development in nine, donor unavailability in seven, disease relapse in three, and secondary malignancy in one patient, respectively. Nine patients were still on treatment with DLI, and they received a median of four (range 2–12) doses. Fourteen percent of patients developed transient grade-II acute GVHD while 12% developed chronic GVHD post-DLI administration. Acute GVHD was managed successfully with short course steroids, and four out of five patients with cGVHD were disease-free and off immunosuppression. With a median follow-up of 44 months (range 8–120), relapse-free (RFS) and overall survival (OS) were 74%, (95% CI, 54–87%) and 78%, (95% CI, 58–89%) respectively, while the cumulative incidence of non-relapse mortality (NRM) was 13% (95% CI, 4–28%). The cumulative incidence of relapse in patients with intermediate and high DRI is 7% and 15%, respectively. Conclusion: Prolonged—up to three years—low-dose pro-DLI administered every two months is safe and effective in reducing relapse rate in patients with high-risk acute leukemia. The low-dose repetitive administration DLI strategy reduced the risk of DLI-mediated GVHD, while the prolonged repeated administration helped in preventing relapse, possibly by inducing a sustained and prolonged immunological pressure on residual leukemic cells. This novel strategy deserves testing in larger cohort of patients with high-risk acute leukemia.

Transplant-associated thrombotic microangiopathy (TMA) occurs in a significant percentage of patients after allogeneic stem cell transplantation (allo-SCT) and is associated with significant morbidity and mortality. The aim of the present study was to examine the association of serum angiopoetin-2 (Ang2) levels and the presence of antibodies against angiotensin II type 1 (AT1R) and ndothelin A Recreptor (ETAR) with the outcome of patients with TMA and/or graft-versus-host disease (GVHD) after allo-SCT. Analysis of our data showed that elevated serum Ang2 levels at the time of TMA diagnosis are significantly associated with increased non-relapse mortality and decreased overall survival. To our knowledge, this is the first study demonstrating an association between raised Ang2 levels and poor outcomes in patients with TMA. Antibodies against AT1R (AT1R-Abs) and ETAR (ETAR-Abs) were detected in 27% and 23% of the patients, respectively, but there was no association between the presence of autoantibodies and the outcome of patients with TMA. However, a significant finding was the strong positive correlation between the presence of AT1R-Abs with the occurrence of chronic fibrotic GVHD, such as scleroderma and cryptogenic organizing pneumonia, raising the possibility of the contribution of autoantibodies in the pathogenesis of fibrotic GVHD manifestations.

Bacterial infections, especially bloodstream infections (BSIs), compromise the overall survival of patients with hematological malignancies undergoing cellular therapies. The interplay between rectal colonization by different types of multidrug-resistant organisms (MDRO) and subsequent BSIs is not fully determined. We aimed to describe the natural history and risk factors for colonization by MDRO, as well as its impact on subsequent BSIs in patients treated with cellular therapies in an environment of antimicrobial resistance. Retrospective, single-center cohort study of consecutive adult hematological malignancies patients treated with allogeneic or autologous hematopoietic cell transplantation (HCT) or chimeric antigen receptor T-cell therapy between 2021 and 2024 in Attikon University Hospital (Greece), with ≥1 available rectal screening test for carbapenem-resistant gram-negative bacilli (CR-GNB) and vancomycin-resistant Enterococcus faecium (VRE). Univariate and multivariate Cox regression were implemented for identifying predictors of CR-GNB and VRE colonization. We also studied the concordance between rectal colonization and subsequent BSIs. One hundred eighty-two patients were included (male: 64%, mean age: 50.2 ± 13 yr, acute myeloid leukemia/myelodysplastic syndrome diagnosis: 55%, relapsing/refractory disease: 58%, allogeneic HCT: 85%). Median duration of hospitalization and neutropenia was 35 and 15 d, respectively. At baseline, 95% of patients were negative on rectal screening for both CR-GNB and VRE, and of those, 8.4% and 23% were colonized with CR-GNB and VRE during follow-up, respectively. Prior colonization with the same pathogen was independently associated with subsequent CR-GNB (HR: 13.0, 95% CI: 2.83 to 59.3) and VRE (HR: 4.83, 95% CI: 2.28 to 10.2) colonization. Seventy-nine patients had ≥1 BSIs (gram-positive: 60%, gram-negative: 38%), with three concordant CR-GNB BSIs among 16 colonized patients (18.7%) and two CR-GNB BSIs among 153 noncolonized patients (1.3%). Regarding VRE, we identified two concordant BSIs among 45 colonized patients (4.4%). Despite the high MDRO prevalence, we observed low rates of CR-GNB colonization in neutropenic patients treated with cellular therapies, with one patient out of five experiencing a concordant CR-GNB BSI. VRE colonization was more frequent, but it rarely resulted in a concordant BSI. These findings highlight the importance of infection control strategies and support de-escalation approaches in empirical antibacterial treatment of febrile neutropenia in this vulnerable population.