Conversion Surgery for Advanced Thoracic SMARCA4-Deficient Undifferentiated Tumor With Atezolizumab in Combination...

A SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a rapidly progressing subtype of lung cancer with a poor prognosis and causes early postoperative recurrence among operable patients. In this study, we present a case of SMARCA4-UT with vertebral and chest wall invasion that successfully underwent conversion surgery after treatment with atezolizumab in combination with bevacizumab, paclitaxel, and carboplatin. The surgical specimen comprised SMARCA4-deficient and SMARCA2-positive adenocarcinoma, confirming intratumor heterogeneity. Gene panel analysis revealed no substantial differences in mutant gene profiles among tumors and no differences in SMARCA2 mutations. Furthermore, no recurrence occurred for 9 months after surgery. Thus, this case illustrates the possibility of multidisciplinary treatment including neoadjuvant therapy with immunotherapy and conversion surgery for SMARCA4-UT.