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P1.13-32 Comparison Between Immune-Mediated Pneumonitis and Pneumonia in Patients Treated with PD-1/PD-L1 Therapy

      Background

      Immune-mediated pneumonitis (IMP) is an uncommon but potentially fatal toxicity of anti–programmed death-1 (PD-1)/programmed death ligand 1 (PD-L1) therapy for non-small cell lung cancer. The purpose of study was to compare clinical and radiographic findings between IMP and pneumonia by pathogen.

      Method

      From 2014 to 2017, a total of 154 patients who received anti–PD-1/PD-L1 therapy were identified. Among these, IRP developed in 9 (5.8%) and pneumonia in 30 (19.5%), which were confirmed through multidisciplinary approach. CT findings (reticulation, consolidation, ground glass opacity [GGO], interlobular septal thickening, micro- [<10mm] and macro-nodules [≥10mm], bronchial wall thickening, bronchiectasis, pleural effusion, and lesion distribution/bilaterality) and clinical features (symptom, smoking history, cancer staging, laboratory findings, underlying disease, prior radiotherapy history) were compared between IRP and pneumonia. Grade and outcome of IRP were also investigated.

      Result

      In chest CT, diffuse reticulation (44.4% vs.0%, P=0.02), patchy/diffuse GGO (100% vs. 50%, P=0.01), and interlobular septal thickening (66.7% vs. 10%, P=0.002) were significantly more frequent in IRP than in pneumonia, whereas macronodule (0 vs. 36.7%, P=0.033) was significantly more common in pneumonia than IRP. IRP significantly showed peripheral location (77.8% vs. 16.7%, P=0.001) and bilateral distribution (44.4% vs. 3.3%, P=0.007). However, there were no significant differences in clinical findings between IRP and pneumonia. Among the IRP patients, 66.7% (6 of 9) of cases were grade 3, and 66.7% improved with drug holding/steroid therapy. The median onset duration of IRP from the first prescription was 126 days (range, 40-669), the median time for improvement was 43 days (range, 21-45), and the median time to death due to IRP was 18 days (range, 11-55).

      Conclusion

      Several CT findings including diffuse reticulation, patchy/diffuse GGO, and interlobular septal thickening with bilateral and peripheral distribution were more frequent in IRP than pneumonia by pathogen. Clinical findings were overlapped.

      Keywords

      immune-mediated pneumonitis, lung cancer, Immunotherapy