Resistance to ALK inhibitors in ALK-rearranged NSCLC is known to result from secondary mutations such as gatekeeper mutations or the emergence of fusion-negative tumor cells.36-38 Therefore, we conducted plasma NGS (Guardant360) in the patient with CTNNA1-ALK fusion–positive parotid adenocarcinoma at disease progression after he was treated with alectinib. The gene discussed is CTNNA1; the disease is non-small cell lung carcinoma.