High level of C-reactive protein as a predictive factor for immune-related adverse events of immune checkpoint inhibitors in non-small cell lung cancer: a retrospective study.

Background: Several risk factors for the immune-related adverse events (irAEs) during treatment with immune checkpoint inhibitors (ICIs) have been reported, of which include high levels of C-reactive protein (CRP). In this study, we aim to evaluate CRP levels before ICIs treatments as potential predictive biomarkers of irAEs incidence rate and overall survival (OS) in patients with advanced non-small cell lung cancer (NSCLC).

Methods: Between December 1, 2015 to December 31, 2019, we retrospectively collected all adult patients with NSCLC who received at least one dose of an ICI targeting the PD-1/PD-L1 axis at the Iwate Medical University Hospital in Japan. In this study the patients were categorized into low and high groups with a cut-off value of 10 mg/L as the baseline level of CRP before the ICI treatment. The primary endpoint was relationship between CRP levels at baseline and incidence of irAEs. The secondary endpoints were the relationship of progression-free survival (PFS) and OS.

Results: A total of 101 irAEs, and 25 severe irAEs were observed. The incidence of the most irAEs was higher in the high CRP group compared to the low CRP group (54.4% 34.5%, respectively, P=0.003). The most frequent irAEs were skin rush (28.8%), followed by pneumonitis (19.2%), hypothyroidism (15.4%), and hepatotoxicity (9.6%). The most common grade 3 or 4 irAEs was pneumonitis (7.9%), which tended to be more frequent in the high CRP group. In multivariate analysis, patients with high CRP levels had an adjusted OR of 2.41 and were associated with an increased risk of developing irAEs (95% CI: 1.16-4.43, P=0.020). The high CRP group was related with shorter PFS compared to the low CRP group (2.2 3.3 months, respectively, P=0.006). The high CRP group were also related with shorter OS compared to the low CRP group (8.9 39.1 months, respectively, P<0.001).

Conclusions: The results suggest that higher level of pretreatment CRP is involved in the development of irAE and poor prognosis. Identification of patients at high risk of irAEs would be of great help. Future multicenter prospective studies are needed to expand on this study.