Impact of Checkpoint Inhibitor Immunotherapy, Primarily Pembrolizumab, on Infection Risk in Patients with Advanced Lung Cancer: A Comparative Retrospective Cohort Study

Background: Checkpoint inhibitor (CPI) immunotherapy has revolutionized cancer treatment. However, immune-related adverse events and the risk of infections are not well studied. To assess the infectious risk of CPIs, we evaluated the incidence of infections in lung cancer patients treated with CPIs plus conventional chemotherapy (CC) vs CC alone. Methods: We performed a retrospective comparative study of patients with advanced non-small cell lung cancer who received CPIs combined with CC and those treated with CC alone at our institution during January 2016 to February 2019. We compared clinical characteristics, treatments, and outcomes including infection rate and mortality between the groups. Results: We identified 123 patients for the CPI group and 147 patients for the control (CC) group. Eighteen patients (15%) in the CPI group and 33 patients (22%) in the control group developed infections (P=.1). Pneumonia was the most common infection encountered in both groups. Urinary tract infection was higher in the CC group (40%) than in the CPI group (9%) (P=.01). On multivariable analysis, chronic obstructive pulmonary disease (P=.024), prior use of corticosteroids (P=.021), and neutropenia (P<.001) were independent risk factors for infection and severe infection requiring hospital admission. Chronic kidney disease (P=.02), prior cancer treatment (P=.023), and neutropenia (P<.0001) were identified as independent risk factors for all-cause mortality. Conclusions: Lung cancer patients treated with CPIs combined with CC have a comparable risk of infection to those treated with CC alone, although there is a trend towards fewer infections in those given CPIs, particularly when it comes to urinary tract infections.