NCOG-21. EFFECT OF PNEUMOCYSTIS JIROVECII PNEUMONIA PROPHYLAXIS ON HEMATOLOGIC TOXICITY IN PATIENTS RECEIVING CHEMORADIATION FOR PRIMARY BRAIN TUMORS

Abstract

Abstract INTRODUCTION Management of diffuse gliomas often includes radiation plus concomitant and adjuvant temozolomide. Hematologic toxicities are common from this therapy. Patients frequently receive prophylaxis against pneumocystis jirovecii pneumonia (PJP) during chemoradiation; however, some PJP prophylaxis drugs have the potential to independently cause myelosuppression which could exacerbate the hematologic toxicities from chemoradiation requiring chemotherapy dose reduction or cessation. We seek to understand differences in the frequency of hematologic toxicities during chemoradiation when either trimethoprim/sulfamethoxazole (TMP/SMX) or pentamidine are used for PJP prophylaxis. METHODS This was a retrospective chart review of patients with primary brain tumors who were treated with first-time radiation and concurrent temozolomide between April 2014-August 2021 at the Huntsman Cancer Institute. Chi squared analysis was used to evaluate effect of choice of PJP prophylaxis on risk for neutropenia, lymphopenia, or thrombocytopenia within one month of finishing chemoradiation. Logistic regression was performed to evaluate the effect of PJP prophylaxis on the Common Terminology Criteria for Adverse Events (CTCAE) score for the lowest neutrophil, lymphocyte, and platelet count. RESULTS 217 patients were included in analysis. 144 patients received TMP/SMX, 69 received pentamidine, 1 received dapsone, and 3 received no prophylaxis at initiation of chemoradiation. Of patients who received TMP/SMX, 15.4% developed an absolute neutrophil count < 1,500 cells/µL while this occurred in 7.2% of patients receiving pentamidine (p=0.10). Platelet count < 100,000 occurred in 18.1% of patients who received TMP/SMX and 20.3% of patients who received pentamidine (p=0.70). Worst CTCAE scores for hematologic toxicities were similar between PJP prophylaxis groups. CONCLUSION Our study provides preliminary evidence that the type of PJP prophylaxis does not appear to significantly impact risk for hematologic toxicity in patients receiving radiation and concurrent temozolomide; however, there was a trend toward higher rates of neutropenia with TMP/SMX and larger analyses are needed to further evaluate these findings.