(PA-135) Evaluating the Efficacy and Tolerability of PJP Prophylaxis with TMP-SMX in Autologous Stem Cell Transplants for Lymphoma or Myeloma: A Retrospective Cohort Study

Introduction:  Patients undergoing allogeneic (HSCT) and autologous stem cell transplantation (ASCT) are at increased risk of Pneumocystis jirovecii pneumonia (PJP). Trimethoprim-sulfamethoxazole (TMP-SMX) is recommended as PJP prophylaxis for patients undergoing HSCT; its routine use in ASCT is debated. The aim of this study is to evaluate the efficacy and safety of TMP-SMX prophylaxis post-ASCT, facilitated by local practice changes when routine prophylaxis was implemented in October 2020.

Methods:   This retrospective study included consecutive adults undergoing ASCT for myeloma or lymphoma. Outcomes were compared between two cohorts: patients prescribed PJP prophylaxis with TMP-SMX for 3 months, and those who were not prescribed prophylaxis. The primary outcomes were rate of PJP infection and all-cause mortality at 3 months post-ASCT. Secondary outcomes included rates of PJP-related mortality, transfusion, rehospitalization, adverse effects and adherence. Laboratory values were collected prior to starting prophylaxis, at 1- and 3-months post-ASCT.

Statistical analyses were performed using proportion or Fisher’s exact tests for categorical variables, and t-tests, Wilcoxon-Mann-Whitney, Negative Binomial Regression or ANOVA for continuous variables with RStudio (v1.4.1717).

Results:   A total of 199 patients were included, with 86 in the TMP-SMX prophylaxis cohort (median age 64, range 22-75), and 113 in the no prophylaxis cohort (median age 63, range 34-75). Rate of adherence to TMP-SMX prophylaxis was 87%. Reasons for discontinuation included neutropenia (3), pancytopenia (1), gastrointestinal effects (3), rash (1), dyspnea (1), and missed prescriptions (2).

No cases of PJP occurred in the no prophylaxis cohort. There was 1 case of presumed PJP infection in the prophylaxis cohort in a patient who stopped prophylaxis due to intolerance. There was no significant difference in all-cause mortality between cohorts in the first 3 months post-ASCT. There were no PJP-related deaths.

There were 24 infections in prophylaxis cohort and 36 infections in no prophylaxis cohort (P=0.88). Rate of rehospitalization was 10% higher in the prophylaxis cohort (P=0.048), with no differences in length of hospitalization per patient (P=0.28) or rate of ICU admission (P=0.66).

There were no significant differences in hemoglobin, platelet, and neutrophil levels between cohorts (P >0.20). Similarly, no significant differences were observed in red blood cell and platelet transfusions during the first month between the cohorts (P=0.06, 0.74 respectively). There was 1 case of acute kidney injury in the prophylaxis cohort and 2 cases in the no prophylaxis cohort.

Conclusions:   TMP-SMX can be considered in post-ASCT where it is well tolerated with minimal adverse events and high rates of adherence. Further study with a larger prospective population is needed to capture sufficient cases of PJP and determine the impact of TMP-SMX prophylaxis on reducing PJP-related morbidity and mortality.