Low lymphocyte counts and association with clinical outcomes in hospitalized patients with cancer receiving immune checkpoint inhibitor therapy.

Abstract

e14600 Background: Immune checkpoint inhibitors (ICIs) improve survivals in a variety of cancer patients by harnessing the immune system. Pre-treatment lymphopenia as measured by absolute lymphocyte counts (ALC) was associated with decreased progression-free survival (PFS) and overall survival (OS) in patients receiving ICIs. During hospitalization ICI treatment is often deferred and efficacy in this population is unclear. Our study explores outcomes and predictive factors for hospitalized patients who received ICI therapy. Methods: Cancer patients who received inpatient ICI were identified in the institutional pharmacy database from 08/2016 to 07/2021. Data were abstracted from electronic medical records. Data were summarized according to frequency and percentage for qualitative variables, and by mean ± standard deviation, median, and range for quantitative variables. The 95% confidence interval for survival was calculated using the exact binomial distribution. PFS and OS were estimated using the Kaplan–Meier method and compared using the log-rank test between groups. Receiver-operating characteristic (ROC) analysis was used to evaluate the discrimination ability of ALC for prognosis. Statistical significance was defined as 2-sided P < 0.05. Results: Of 37 identified patients, 2 were excluded from the ALC analysis due to lack of blood counts. The most common cancer type treated was lung cancer (13, 35.1%). The majority of subjects were men (29, 78.4%) and the median age was 57 (21-79) years. Average hospital stay was 24.2 (95% CI 16.5, 31.9) days, and the most common reasons for admission were initiation of therapy (14, 37.8%) and infection (5, 13.5%). Reasons for inpatient treatment included convenience (6, 16.2%), disposition delays (6, 16.2%), initiation of therapy (13, 35.1%), and emergent or last resort measures (10, 27.0%). Most patients died during the study period, and 5 were alive at the time of data analysis. 10 patients died during the same hospitalization as treatment. Of those who followed up, 22 died within 90 days of inpatient therapy. The median PFS was 0.86 (95% CI 0.43, 1.74) months and median OS was 1.55 (95% CI 0.76, 3.72) months. Pre-treatment ALC < 600 cells/µL were associated with poor PFS (0.33 vs. 1.35 months; HR 6.9, 95% CI 10.8-25.9, P = 0.0053) and poor OS (0.33 vs. 2.34 months; HR 4.66, 95% CI 1.2-17.5, P = 0.0236), respectively. Furthermore, patients with ALC < 600 were less likely to receive a subsequent ICI dose than their counterparts. Conclusions: Administration of inpatient ICI therapy is associated with poor clinical outcomes and high rates of both inpatient mortality and death within 3 months of discharge. The presence of ALC < 600/µL in hospitalized patients was associated with poor clinical outcomes.