Fig. 1. Chest CT images for Case 1.
A, B. Chest CT at 8 weeks of nivolumab therapy demonstrated new GGO, reticular opacities, and consolidation in lower lobes predominantly on the left, with a peripheral and lower distribution, radiographically representing a COP pattern (arrows). C–D. On chest CT at 15 weeks of therapy, the findings significantly increased and involved all lobes, with multifocal areas of GGO, reticular opacities, and consolidation (arrows), as well as centrilobular nodularity and traction bronchiectasis in predominantly peripheral distribution. The overall features demonstrated a COP pattern, while the progressive nature was also indicative of developing ARDS.
E–F. Further follow-up CT after 4 weeks of prednisone treatment showed a significant decrease of the CT findings with residual GGOs, demonstrating a “reversed halo” sign with central GGO surrounded by dense air-space consolidation of crescentic shape (F, arrows), which has been reported as a radiographic manifestation of COP.
G–H. Chest CT scan 4 weeks after the completion of prednisone treatment showed a development of dense consolidations with GGOs and reticular opacities (arrows) in peripheral and multifocal distributions, involving both upper and lower lobes, again demonstrating COP pattern as noted during the first episode of PD-1 pneumonitis. Given the similarity of radiographic and clinical manifestations with the 1st episode, the patient restarted prednisone for treatment of a “pneumonitis flare”.
I–J. Follow-up chest CT taken 2 weeks after starting the 2nd course of prednisone therapy demonstrated decrease of consolidation and GGOs (arrows), indicating improving pneumonitis in response to corticosteroid therapy.