Clinical case of lung spindle cell carcinoma markedly responsive to pembrolizumab

A 52‐year‐old man underwent pneumonectomy of the left lung for previously diagnosed primary spindle cell carcinoma (pT4aN1M0, stage III B) with programmed death‐ligand 1 expression (tumor proportion score ≥95%) and without epidermal growth factor receptor gene mutation and anaplastic lymphoma kinase fusion gene. However, brain metastasis and chest wall tumor relapse occurred. Considering insufficient improvement with gamma knife treatment for brain metastasis and combination chemotherapy (paclitaxel, carboplatin, and bevacizumab), pembrolizumab monotherapy and palliative irradiation therapy for chest metastases were started after brain tumor volume reduction using craniotomy. Brain edema and chest wall metastases markedly improved following a pseudoprogression of the brain edema accompanied by a performance status decline; this effect continued until 11 cycles of pembrolizumab administration.