Utility of the NLR and the ratio of NLR after and before adverse events for identifying irAEs and bacterial infections in patients with cancer during PD-(L)1 inhibitors treatment.

e14620 Background: Identifying immune-related adverse events (irAEs) or bacterial infections in cancer patients undergoing treatment with PD-(L)1 inhibitors can be challenging. This study aimed to assess the effectiveness of the neutrophil-to-lymphocyte ratio (NLR) in distinguishing between irAEs and bacterial infections in cancer patients receiving PD-(L)1 inhibitors. Methods: We conducted a retrospective analysis of cancer patients who received at least one dose of PD-(L)1 inhibitors at Affiliated Cancer Hospital of Zhengzhou University from 2018 to 2023. We compared the changes in peripheral blood cell counts before and after the occurrence of adverse events, as well as the ratio of the NLR at the time of adverse events (post-NLR) to the NLR before adverse events (pre-NLR). Bacterial infections were diagnosed based on clear etiology and/or controlled adverse events through the use of antibiotics without systemic glucocorticoid administration during treatment. irAEs were diagnosed based on clinicolaboratory criteria, or the improvement of immune system disorders after withdrawal of PD-(L)1 inhibitors or systemic glucocorticoid administration, excluding bacterial infection. Data were collected from microbiology, radiography, serology, and physician notes. Results: Among the 4173 patients who were administered PD-(L)1 inhibitors, 217 individuals experienced a total of 249 irAEs, while 256 patients were diagnosed with 257 bacterial infections. When comparing pre-infection levels with those after bacterial infection, it was observed that the NLR increased significantly. Similarly, in the group experiencing irAEs, the NLR also showed a significant increase after the occurrence of the irAEs. Notably, the NLR was significantly higher in patients with bacterial infections compared to those with irAEs [11.08 (6.63, 19.29) vs 2.78 (1.92, 4.31), P < 0.001]. Furthermore, the post-NLR/pre-NLR ratio was higher in the bacterial infection group than in the irAEs group [2.86 (1.56, 6.20) vs 1.16 (0.82, 1.76), P < 0.001]. Appraising the potential of NLR and the post-NLR/pre-NLR ratio in identifying irAEs and bacterial infections in cancer patients, the receiver operating characteristic (ROC) curve analysis was performed. The area under the curve (AUC) was 0.91 for NLR and 0.81 for the post-NLR/pre-NLR ratio, respectively. Using a cut-off value of 4.56 for NLR and 1.96 for the post-NLR/pre-NLR ratio yielded the highest sensitivity and specificity. Conclusions: The NLR along with the post-NLR/pre-NLR ratio could serve as valuable diagnostic indicators for irAEs and bacterial infections in cancer patients undergoing treatment with PD-(L)1 inhibitors.