Characteristics and risk factors for microbial infections during cancer immune checkpoint therapy

The risk of infection in patients receiving immune checkpoint inhibitor (ICI) therapy is not well understood. Immune-related adverse events requiring immunosuppressive therapy may impact infection risk. ICIs may induce an exaggerated immune response to latent infection. We assessed the incidence and risk factors for infections during cancer ICI therapy. A retrospective chart review of solid tumor patients treated with ICIs was conducted. Infectious episodes were defined as those where a microbial organism was cultured or identified through polymerase chain reaction. Infections which occurred during and up to 1 year following ICI therapy were considered "post-ICI" infections. Of 327 patients, 47% had melanoma and 36% had non-small cell lung cancer. The majority (77%) received single agent anti-PD(L)1 antibody, 14% received combination anti-PD(L)1 and anti-CTLA4 antibody, and 9% single agent anti-CTLA4 antibody. Infections occurred in 89 (27%) in the post-ICI compared with 111 (34%) patients in the pre-ICI period (p = 0.57). The most common types of infection were respiratory, genitourinary, and cutaneous infections. On multivariate analysis, only age over 67 years significantly predicted for development of infection on ICI (HR 1.73, p = 0.04). We did not find receipt of corticosteroids, combination ICI therapy, diabetes, or gender to significantly impact on infection risk. The rate of microbial infections among solid tumor patients receiving ICI therapy was 27%, comparable to the infection rate of 34% in the same cohort of patients in the period pre-ICI therapy. Age over 67 years was significantly associated with infection post-ICI.