SMARCA4-deficient undifferentiated tumors (SMARCA4-UTs) are rare, aggressive thoracic malignancies with dismal prognosis. Most cases are refractory to conventional therapy, a significant number of patients show no response to one or more chemotherapy regimens, exhibiting an overall survival (OS) of less than six months. We report a case of a 52-year-old male heavy smoker with a right lower lobe SMARCA4-UTs harboring TP53 mutation and PD-L1 expression (tumor proportion score TPS 30%, combined positive score CPS 30%). The tumor showed loss of SMARCA4 (also known as BRG1), high Ki-67 (∼50%), and rapid growth. After six cycles of tislelizumab+paclitaxel/cisplatin, the lesion demonstrated partial remission and progressive cavitation on CT imaging. Consolidative radiotherapy (60 Gy/30 fractions) further reduced the tumor burden. The survival period of this patient was 17 months long. This case highlights that PD-L1 expression and radiologic cavitation may serve as potential efficacy biomarkers in SMARCA4-UTs, even in tumors with TP53 mutations and a high proliferative index. Combined immunotherapy with chemotherapy and radiotherapy may confer durable disease control in this aggressive lung cancer subtype. • This case highlights that PD-L1 expression and radiologic cavitation may serve as markers of efficacy in SMARCA4-UT, even in tumors with TP53 mutation and high proliferative index. Combined immunochemotherapy and radiotherapy may provide durable disease control in this aggressive lung cancer subtype.
DENG et al. (Sun,) studied this question.