Thoracic SMARCA4-Deficient Undifferentiated Tumor With ALK Fusion Treated With Alectinib Achieved Remarkable Tumor Regression: Case Report

Recently, SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) has emerged as a distinct subset of lung cancer. Previous studies have suggested that SMARCA4-UT is often associated with smoking-related mutations, such as KRAS and STK11, rather than EGFR or ALK alterations. Nevertheless, no specific precision therapy has been identified for SMARCA4-UT. Here, we report the first case of concomitant ALK rearrangement and SMARCA4 (BRG1) deficiency in a nonsmoking female with thoracic cancer. Alectinib was given as the first-line therapy, and the patient achieved a remarkable complete response. Our case highlights the significance of ALK rearrangement identification for the precise therapeutic potential of SMARCA4-UT.