Procalcitonin level threshold and antibiotic use in patients receiving chimeric antigen receptor T-cell therapy.

Background: Patients undergoing chimeric antigen receptor (CAR) T-cell therapy are vulnerable to infection and sepsis. Treatment course is frequently complicated by cytokine release syndrome which is often clinically and biochemically indistinguishable from sepsis. Procalcitonin (PCT) levels have been examined as a promising biomarker for infection in this cohort of patients.

Methods: In this study, we measured daily PCT levels for patients for fourteen days (or hospital discharge) after receiving CAR T-cells to determine threshold PCT values specific for infection compared to those without infection.

Results: We present preliminary results of our enrolled cohort to date (sixteen patients). Infection was present in only 12.5% of patients. However, those diagnosed with sepsis had elevated PCT levels with a peak mean of 2.6 µg/L observed on the seventh day post-treatment compared to those without infection remaining below 0.5 µg/L. Furthermore, we observed a trend for early and liberal antibiotic administration within our cohort.

Conclusion: Our study highlights the challenges of antimicrobial stewardship in managing CAR T-cell therapy recipients. Our preliminary results underscore the utility of PCT in the risk-stratification and diagnosis of those patients at high risk for infectious complications after receiving CAR T-cell therapy and continue to advocate for a PCT threshold of 1.5 µg/L for diagnosing sepsis. Additionally, in the setting of CRS and lymphodepletion, where white cell count and CRP value are unreliable, a PCT value of < 0.5 µg/L may help exclude sepsis.