Trimethoprim-Sulfamethoxazole versus Aerosolized Pentamidine for PJP Prophylaxis after Allogeneic Hematopoietic Cell Transplantation: Association with Bacterial Infections and Survival.

BACKGROUND: Trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line prophylaxis for Pneumocystis jirovecii pneumonia (PJP) after allogeneic hematopoietic cell transplantation (allo-HCT). Aerosolized pentamidine (AP) is commonly used as an alternative in patients intolerant to TMP-SMX. However, the comparative impact of these strategies on non-PJP infections and transplant outcomes remains unclear. METHODS: We retrospectively analyzed 123 allo-HCT recipients who received PJP prophylaxis with TMP-SMX (n = 42) or AP (n = 81) after engraftment. The primary endpoints were the incidence of PJP and documented bacterial infections. Secondary endpoints included risk factors for bacterial infections, safety, and overall survival (OS). RESULTS: PJP incidence was low in both groups, with no cases in the TMP-SMX group and one case in the AP group. The 1-year cumulative incidence of documented bacterial infections was significantly lower in the TMP-SMX group than in the AP group (3.0% vs. 30.4%, p=0.0003). In multivariate analysis, AP use was identified as an independent risk factor for bacterial infections (Odds ratio 12.4; 95% CI 2.46-62.8). Many pathogens isolated in the AP group were susceptible to TMP-SMX. During the observation period, OS did not differ significantly between the TMP-SMX and AP groups (p=0.29). CONCLUSION: TMP-SMX prophylaxis was associated with a reduced risk of bacterial infections compared with AP. TMP-SMX may be considered the preferred option for patients who can tolerate the regimen, and switching from AP to TMP-SMX may be appropriate after recovery from treatment-related toxicities.