Successful treatment with nivolumab for SMARCA4‐deficient non‐small cell lung carcinoma with a high tumor mutation burden: A case report

SMARCA4 is a subunit of the switch/sucrose non‐fermentable (SWI/SNF) chromatin‐remodeling complex. An effective treatment for SMARCA4‐deficient non‐small cell lung carcinoma (NSCLC) has not yet been established. Correlations between a response to immune checkpoint inhibitors and the SWI/SNF complex have been suggested, but little is known about the efficacy of immune checkpoint inhibitors against SMARCA4‐deficient NSCLC. A 43‐year‐old man underwent left upper lobe lung resection and was diagnosed with SMARCA4‐deficient lung adenocarcinoma. Two months after surgery, multiple lung metastases appeared. Immunohistochemical analysis showed no PD‐L1 expression. Whole‐exon sequencing revealed a relatively high tumor mutation burden at 396. After the failure of three standard chemotherapy regimens, the patient was treated with nivolumab as fourth‐line treatment. An obvious reduction in the lung metastases was obtained for more than 14 months. We report the first case of SMARCA4‐deficient NSCLC with a high tumor mutation burden successfully treated with nivolumab. Anti‐PD‐1 antibodies might be a promising treatment strategy for patients with SMARCA4‐deficient NSCLC.