(1570) Impact of Lymphopenia in an Oncology ICU: Characterization and Outcomes

Introduction: Oncology patients, especially those with sepsis, face high mortality due to immunosuppression. While prolonged lymphopenia predicts sepsis mortality, there is limited data on its impact on infection risk and mortality in oncology ICU patients. This study aimed to describe the impact of lymphopenia on superimposed infections and mortality in critically ill oncology patients.

Methods: This is a retrospective cohort study, between January-December 2023, of adult cancer patients admitted to the ICU with sepsis. Data collected included malignancy type, absolute lymphocyte count (ALC), hospital length of stay (LOS), hospital and 90-day mortality, superimposed infections in the ICU, and post-discharge infections. Lymphopenia was defined as ALC < 1 K/µL at ICU admission, with severe lymphopenia as ALC < 0.5 K/µL. Descriptive statistics, Chi-square or Fisher’s exact tests for categorical variables, and Wilcoxon rank sum tests for continuous variables were used. Logistic regression assessed effects on hospital mortality.

Results: A total of 350 patients were admitted with sepsis to the ICU in the study period. The majority of patients were lymphopenic (77.4%), with 69.4% having severe lymphopenia at the time of ICU admission. Incidence of lymphopenia was similar between solid (57.9%) and hematological malignancies (42.1%; p=0.8). There were no differences in types of infections on admission, rates of superimposed infections during hospital stay or discharge, hospital LOS, or mortality between lymphopenic and non-lymphopenic patients. No differences in superimposed infections or mortality were seen when further stratifying patients by ALC < 1 K/µL or less than < 0.5 K/µL. Logistic regression modeling found the odds of hospital mortality was 2.5 times higher for patients who had a superimposed infection in the ICU as compared to those without, regardless of ALC.

Conclusions: This study found a high incidence of lymphopenia, however it did not correlate to increased infection rates or mortality in septic, oncology patients. Superimposed infections, while not related to lymphopenia, led to increased mortality. Future studies assessing the chronicity, dynamics, and causality of lymphopenia may help understand the impact of lymphopenia on this patient population.