Risk Factors for Immune Checkpoint Inhibitor-Related Pneumonitis in Cancer Patients: A Systemic Review and Meta-Analysis

<b><i>Background:</i></b> Immune checkpoint inhibitors (ICIs) can lead to one of the common and quite serious immune-related adverse events (irAEs) in a real-world setting, namely, checkpoint inhibitor pneumonitis (CIP). <b><i>Objective:</i></b> We aimed to investigate the potential risk factors for CIP in cancer patients treated by ICIs and quantify the association. <b><i>Methods:</i></b> We conducted a systematic literature review in PubMed, EMBASE, and Web of Science from January 1, 2000, to March 20, 2022, with no study design restrictions. Studies evaluating the risk factors for CIP in cancer patients treated with ICIs-containing regimes were included. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for risk factors of CIP by using random-effect model. Heterogeneity was assessed by sensitivity analysis and subgroup analysis regarding CIP severity, geographical regions, cancer types, treatment regimes, and ICI types. <b><i>Results:</i></b> A total of 35 studies comprising 142,703 patients were eventually included. The incidence of grade I–V and grade III–V CIP in cancer patients was 0.16 (95% CI: 0.14–0.18) and 0.06 (95% CI: 0.05–0.08), respectively. When combining the adjusted ORs, the following risk factors were significantly associated with the development of CIP: squamous cell carcinoma (OR: 1.31, 95% CI: 1.18–1.45), previous thoracic radiotherapy (OR: 2.07, 95% CI: 1.34–3.19), preexisting radiation-induced pneumonitis (OR: 3.62, 95% CI: 1.53–8.58), preexisting respiratory disease (OR: 2.43, 95% CI: 1.45–4.07), preexisting interstitial lung disease (OR: 5.78, 95% CI: 3.08–10.85), preexisting ground glass attenuation (OR: 11.48, 95% CI: 1.13–116.74), preexisting honeycombing (OR: 6.11, 95% CI: 2.37–15.79), preexisting pulmonary emphysema (OR: 2.72, 95% CI: 1.00–7.36), use of pembrolizumab (OR: 2.89, 95% CI: 1.56–5.35, <i>I</i>² = 0%), high PD-L1 expression (OR: 3.59, 95% CI: 1.23–10.50), and hypoalbuminemia (OR: 0.3, 95% CI: 0.14–0.64). When including the crude ORs, smoking history (OR: 1.39, 95% CI: 1.14–1.71), neutrophil-lymphocyte ratio (OR: 1.04, 95% CI: 1.01–1.08), and c-reactive protein (OR: 1.08, 95% CI: 1.01–1.16) were also risk factors for CIP. <b><i>Conclusion:</i></b> Histological characteristics, specific previous lung diseases and treatment history, treatment regimen, PD-L1 expression level, and serological biomarkers are all closely associated with the development of CIP. These findings would be useful for oncologists to optimize the appropriate options of ICIs and close monitoring during immunotherapy treatments, particularly for patients identified as having a higher risk for CIP.