Abstract Background: Pneumocystis jirovecii pneumonia (PJP) is a serious respiratory infection that can have significant morbidity and mortality in immunocompromised patients. Patients with hematologic malignancies (HM) inherently have immune dysfunction and are further immunocompromised by anti-neoplastic therapeutics. While some guidelines exist to guide prophylaxis against PJP for these patients, there are many scenarios that these guidelines do not address, such as in patients being treated with newer chemotherapeutic agents or cellular therapies. Additionally, the first-line antimicrobial agents for PJP prophylaxis can have undesirable toxicities among HM patients, leading to use of second-line agents and risk for “breakthrough” PJP. We sought to determine the true incidence of PJP among HM patients at our institution and identify the risk factors for these infections. Methods: Laboratory records of all positive Pneumocystis jirovecii results from Jan 1, 2015 to Mar 1, 2025 at Montefiore were reviewed. We conducted full chart reviews for all patients with both HM and positive PJP results. Data collected included severity of infection, underlying comorbidities and prior treatments, timing of infection relative to stem cell transplant or certain chemotherapies, PJP prophylaxis prior to infection, and mortality relative to PJP. Results: From 457 positive Pneumocystis jirovecii results, we identified 55 adult patients with various HM. The most common malignancies included diffuse large B-cell lymphoma, multiple myeloma, acute myeloid leukemia, and adult T-cell leukemia/lymphoma. Many of these patients had undergone advanced, immunomodulatory treatments, including 11 (20%) with hematopoietic cell transplantation, 3 (5.5%) with chimeric antigen receptor T-cell therapy, 2 (3.6%) with bispecific T-cell engager therapy, and 16 (29%) with rituximab. Six of the 55 patients (10.9%) were on PJP prophylaxis at the time of infection, including 4 (7.3%) on atovaquone and 2 (3.6%) on trimethoprim-sulfamethoxazole. Twenty-three patients (41.8%) died within a year of PJP diagnosis, with a median time from PJP to death of 19 days (+/- 81 days). Conclusions: Recent advances in chemo-immunotherapy have drastically altered the treatment landscape for HM, often inducing profound immunosuppression. Our study highlights the importance of optimizing PJP prophylaxis among these patients, particularly those undergoing treatment with novel therapies. Most of the patients were not on PJP prophylaxis at the time of diagnosis, underscoring the need to further refine the institutional guidelines on criteria for prophylaxis. Ongoing research is comparing this sample to a control group of patients with HM who did not develop PJP in order to further identify risk factors and develop clearer, evidence-based prophylaxis guidelines.
Orner et al. (Mon,) studied this question.