Utility of the neutrophil-to-lymphocyte ratio and the ratio of neutrophil-to-lymphocyte ratio after and before adverse events for differential diagnosis of immune-related adverse events and bacterial infections in cancer patients treated with PD-(L)1

Differential diagnosis of immune-related adverse events (irAEs) or bacterial infections is sometimes very difficult in cancer patients undergoing treatment with PD-(L)1 inhibitors. 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. We conducted a retrospective analysis of cancer patients who received at least 1 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 ratios of the NLR that were closest after the occurrence of adverse events (post-NLR) to the NLR that were closest before the occurrence of adverse events (pre-NLR). 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. The post-NLR increased significantly compared with pre-NLR in patients with bacterial infection (P < 0.001), while the post-NLR had smaller increase compared with pre-NLR in patients sufffering irAEs (P < 0.001). Notably, the NLR was significantly higher in patients with bacterial infection compared with those with irAEs (P < 0.001). Furthermore, the post-NLR/pre-NLR ratio was higher in the bacterial infection group than in the irAEs group (P < 0.001). 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.