Incidence of Pneumocystis jirovecii pneumonia utilizing a polymerase chain reaction-based diagnosis in patients receiving bendamustine

Background: Pneumocystis jirovecii pneumonia (PJP) is a life-threatening infection occurring in patients receiving bendamustine. The poorly defined incidence, particularly when utilizing polymerase chain reaction (PCR)-based diagnostic techniques, precipitates unclear prophylaxis recommendations. Our objective was to determine the cumulative incidence of PJP diagnosed by single copy target, non-nested PCR in patients receiving bendamustine. Methods: Patients were evaluated for PJP from initiation of bendamustine through 9 months after the last administration. The cumulative incidence of PJP was estimated using the Aalen–Johansen method. Cox proportional hazard models were used to demonstrate the strength of association between the independent variables and PJP risk. Results: This single-center, retrospective cohort included 486 adult patients receiving bendamustine from 1 January 2006 through 1 August 2019. Most patients received bendamustine-based combination therapy (n = 461, 94.9%), and 225 (46.3%) patients completed six cycles. Rituximab was the most common concurrent agent (n = 431, 88.7%). The cumulative incidence of PJP was 1.7% (95% CI 0.8%–3.3%, at maximum follow-up of 2.5 years), after the start of bendamustine (n = 8 PJP events overall). Prior stem cell transplant, prior chemotherapy within 1 year of bendamustine, and lack of concurrent chemotherapy were associated with the development of PJP in univariate analyses. Anti-Pneumocystis prophylaxis was not significantly associated with a reduction in PJP compared to no prophylaxis (HR 0.37, 95% CI (0.05, 3.04), p = 0.36). Conclusions: Our incidence of PJP below 3.5%, the conventional threshold for prophylaxis implementation, indicates routine anti-Pneumocystis prophylaxis may not be necessary in this population. Factors indicating a high-risk population for targeted prophylaxis require further investigation.