C077 | LONG-TERM FOLLOW-UP OF THE BATMO PROTOCOL (BEST-ANTIMICROBIAL-THERAPY-TMO) AND COMPARISON WITH HYSTORICAL DATA

Infectious complications are a major cause of Non-Relapse Mortality (NRM) in allogeneic haematopoietic stem cell transplant (allo-SCT) recipients. Since 2019, our Center has implemented an innovative program called BATMO for infection prevention and management. The main features of this protocol are the absence of fluoroquinolone prophylaxis during the neutropenic phase of allo-SCT, the administration of posaconazole in high-risk patients (pts), and letermovir in CMV-positive pts from day 0 to day +100. We present an update of previously published data (Malagola M et al, Front Oncol 2022), focusing particularly on bacterial and fungal complications within the first 30 days after allo-SCT. We included all pts transplanted at our institution between January 2016 and December 2023, divided into two cohorts: Cohort A (before the BATMO protocol, between 2016 and 2018, 116 patients) and Cohort B (after the BATMO protocol, between 2019 and 2023, 211 patients). The clinical and transplant characteristics of the two cohorts were comparable (table 1), except for a higher number of haploidentical donors in Cohort A (18% vs 30%, p = 0.02) and a greater use of peripheral blood stem cells as the source of hematopoietic stem cells in Cohort B (71% vs 93%, p< 0.05). Notably, a significant reduction of grade II-IV acute Graft Versus Host disease was observed in Cohort B (70% vs 60%, p= 0.03). At day +30, a significantly higher number of patients in Cohort B had at least one episode of bloodstream infection (BSI) (40% vs 56%, p= 0.005), with no differences regarding microbial etiology. This did not lead to differences in overall survival (OS) (figure 1A) and NRM (figure 1B). There was no difference in the number of pts needing carbapenems during neutropenia (43% vs 53%, p= 0.1), but a higher percentage of pts in Cohort B were treated with new antimicrobials (4% vs 28%, p= 0.01), as expected due to the availability of new drugs. No differences in the number of proven/possible invasive fungal disease (p/pIFD) were observed (28% vs 28%, p= 0.9), nor in the number of pts with pneumonia (24% vs 25%, p= 0.7) or enteritis (16% vs 11%, p= 0.14) by day +30. A significantly lower number of cases of fever of unknown origin (FUO) was observed in Cohort B (60% vs 46%, p= 0.01). The results confirm that the BATMO program is safe. In particular, the lack of fluoroquinolone prophylaxis, despite being associated with an increased number of BSIs by day +30, does not impact NRM.