Organizing Pneumonia after Nivolumab Treatment in a Patient with Pathologically Proven Idiopathic Pulmonary Fibrosis.

Acute exacerbation of pre-existing interstitial lung disease (ILD) associated with systemic anticancer therapy is recognized as a life-threatening adverse event of lung cancer treatment. Programmed cell death 1 (PD-1) checkpoint inhibitors, such as nivolumab, often induce pneumonitis in patients with cancer; however, the tolerance and safety of nivolumab for advanced lung cancer with ILD are unclear. We report a 72-year-old patient with lung cancer with pathologically proven idiopathic pulmonary fibrosis who was treated with nivolumab. She demonstrated pneumonitis with an organized pneumonia (OP) pattern, but no acute exacerbation of ILD featuring a diffuse alveolar damage (DAD) pattern. She was successfully treated with corticosteroid therapy, and maintained good disease control after the discontinuation of nivolumab. She also showed pseudoprogression of the primary tumor, implying infiltration of T-cells into the lung. These findings suggest that T-cell activation by nivolumab treatment might not be directly associated with acute ILD exacerbation, and that treatable OP might be a major pulmonary complication of nivolumab in patients with pre-existing ILD, similar to patients without underlying ILD.