Dramatic response to nivolumab after local radiotherapy in pulmonary pleomorphic carcinoma with rapid progressive post‐surgical recurrence

Pulmonary pleomorphic carcinoma (PPC) is resistant to anticancer drug treatment, outcomes are poor, and no standard therapy has been established. High PD‐L1 expression has been found in PPCs, suggesting the possible efficacy of an immune checkpoint inhibitor (ICI) in cancer immunotherapy; however, this approach requires further investigation through case accumulation. Herein, we report a case of rapid recurrence and progression of PPC early after surgery in a 70‐year‐old male ex‐smoker. Surgery was performed for lung cancer of the right lower lobe, and a pathological examination indicated primary PPC with high PD‐L1 expression (tumor proportion score: 90%). Because systemic metastasis recurred only six weeks after surgery, nivolumab was administered as second‐line treatment. Marked tumor regression was observed on imaging after three cycles, revealing a near complete response. Palliative radiotherapy was applied to the bone metastasis region for pain relief before nivolumab was administered. This case suggests that an ICI can have an effect on PPC and that the efficacy of ICIs may be enhanced by radiotherapy‐induced abscopal effects.