Infection-related Hospitalizations During Immune Checkpoint Inhibitor Treatment Without Immunosuppressants.

Immunosuppressants are increasingly being used in the clinic to manage immune-related adverse effects. Consequently, the incidence of secondary infections associated with immunosuppression is increasing. However, little is known about primary infections during immune checkpoint inhibitor (ICI) treatment without immunosuppressants. We aimed to evaluate primary infectious diseases during antiprogrammed death ligand-1 immunotherapy without immunosuppressants. We retrospectively screened medical records of 233 patients who underwent ICI treatment for advanced non-small cell lung cancer between January 2014 and May 2018 at National Cancer Center, Republic of Korea. Subsequently, we evaluated the clinical characteristics and treatment outcomes of selected patients hospitalized for potential infectious disease without immunosuppressive treatment (n=80). Eight cases (3.4%) were identified as bacterial pneumonia (n=5) and cellulitis, inflamed epidermoid cyst, and wound infection (n=1 each). The bacterial pathogens Streptococcus pneumoniae and Haemophilus influenzae were identified in 4 patients with pneumonia. The period between the start of ICI treatment and infection varied between 3 and 189 days (median, 24.5 days). Five (62.5%) patients were infected within a month after ICI treatment initiation. All patients were treated with empirical antibiotics and discharged without complications. The median progression-free and overall survival for ICI treatment was 11.5 and 25.5 months, respectively. Six patients experienced ICI-associated adverse effects postinfection: Herpes zoster infection (n=4) and pneumonitis (n=2). Infectious disease independent of immunosuppression is a rare, but possible event in patients with lung cancer receiving ICI treatment. Clinical awareness would enable prompt diagnosis of primary infection during immunotherapy.