Characterization of Hospital Admissions During Immune Checkpoint Inhibitor Therapy: Insights From the ICOG Study

Immune checkpoint inhibitors (ICI) have improved the therapeutic arsenal in outpatient oncology care; however, data on necessity of hospitalizations associated with immune-related adverse events (irAEs) are scarce. Here, we characterized hospitalizations of patients undergoing ICI, from the prospective cohort study of the immune cooperative oncology group (ICOG) Hannover.

Between 12/2019 and 06/2022, 237 patients were included. Clinical data and characteristics of ICI were collected during a 6-month observation period after the initiation of therapy. Descriptive statistics and Kaplan-Meier statistics were administered.

During the observation period, 30/237 patients were hospitalized (HA(+)). Most common underlying tumor entities were malignant melanoma (59.5%), renal cell carcinoma (13.1%), and nonsmall-cell lung carcinoma (12.7%). HA(+) patients exhibited an increased rate of pulmonary and cerebral metastases. We observed a significantly higher hospitalization rate during dual ICI with Nivolumab and Ipilimumab (p = 0.001). The predominant irAEs for hospitalization were colitis (26.7%), followed by hypophysitis (13.3%), leading to a median hospitalization of 7 (1-34) days. Interdisciplinary consultations were frequent, especially to gastroenterology (46.7%) and neurology (26.7%). Although a trend toward a prolonged overall survival in the HA(+) subgroup was identified, no statistically significant differences were found.

The hospitalization rate of 12.6% is comparable to rates reported in previous studies. There was a disproportionate admission of patients with immune-related colitis and hypophysitis compared to the prevalence described under ICI. We observed a high need for interdisciplinary consultations in line with the heterogeneity of immune-mediated side effects. Compared to non-hospitalized patients, there was no survival disadvantage in the HA(+) cohort.

With a relatively low hospitalization rate, short length of stay, and good clinical outcome, our data support the outpatient nature of ICI. The findings underscore the importance of interdisciplinary collaboration and vigilant monitoring of irAEs to ensure timely recognition and management.