(042) Comparison of Breakthrough Rates of Pneumocystis jiroveci Pneumonia in Adult Patients with Malignancies Receiving Intravenous or Aerosolized Pentamidine for Prophylaxis (Top Ten Poster)

Poster Abstract:

Background: Pneumocystis jiroveci pneumonia (PJP) is an opportunistic infection of the lung, primarily occurring in immunocompromised hosts, including those with cancer. In non-HIV patients with untreated PJP, mortality ranges between 30 to 50%. Although trimethoprim-sulfamethoxazole (TMP/SMX) is the preferred agent for PJP prophylaxis, tolerability, allergic reactions, and drug interactions can pose significant challenges. Pentamidine is often chosen as second-line prophylaxis due to its convenient dosing schedule and tolerability, compared to dapsone or atovaquone. There have been no direct comparisons regarding the efficacy, safety, and cost of intravenous (IV) versus aerosolized pentamidine in patients with cancer.

Objectives: The primary objective of this study is to determine the rate of PJP breakthrough cases among patients with cancer receiving primary prophylaxis with IV or aerosolized pentamidine. Secondary objectives include estimated cost and incidence of adverse effects associated with IV and aerosolized pentamidine.

Methods: This retrospective cohort evaluated adult patients who IV or aerosolized pentamidine for primary PJP prophylaxis between January 1, 2013, and September 30, 2023, at Huntsman Cancer Center. Positive PJP results were identified among IV and aerosolized groups, and charts were analyzed for colonization versus infection. Cost was estimated using wholesale acquisition cost of products. Adverse effects for a randomized 100 patients for each route of administration were assessed via chart review.

Results: A total of 792 patients were identified, 377 (47.6%) of which received IV pentamidine, and 415 (52.4%) received aerosolized pentamidine. Five positive PJP test results occurred while patients were on pentamidine therapy, two (40%) in the IV group and three (60%) in the aerosolized group. Both positive PJP results on IV therapy were determined to be colonization. The three positive PJP test results on aerosolized therapy were determined to be true infections and representative of breakthrough cases. The incidence rate of breakthrough PJP infections on inhaled was determined to be 0.001 per 1000 patient-years. Adverse effects were noted in 11 of the 100 IV patients reviewed. The most common side effect reported was phlebitis which resolved upon slowing of the infusion rate. Seventy-three of the 100 aerosolized patients reviewed had side effects with cough most reported. Cost data is pending.

Conclusion: The incidence of PJP breakthrough cases in adult patients with cancer is low while on pentamidine prophylaxis and does not depend on route. Additionally, the IV formulation had fewer side effects compared to aerosolized pentamidine.

References (must also be included in final poster): 1 - Limper AH. In Search of Clinical Factors that Predict Risk for Pneumocystis jirovecii Pneumonia in Patients without HIV/AIDS [published online ahead of print, 2018 Aug 10]. Am J Respir Crit Care Med. 2018;10.1164/rccm.201807-1358ED. doi:10.1164/rccm.201807-1358ED

2 – "Prevention and Treatment of Cancer-Related Infections.” NCCN, https://www.nccn.org/professionals/physician_gls/pdf/infections.pdf. Accessed August 13, 2023.

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