Abstract: This invention provides a therapeutic method for treatment of EGFR gene mutation-positive lung cancer using the REIC/Dkk-3 gene in combination with the EGFR tyrosine kinase inhibitor, the PD-1/-L1 immune checkpoint pathway inhibitor, and/or the molecular-targeted agent. This invention provides a therapeutic agent comprising, as an active ingredient, the REIC/Dkk-3 gene, which is used in combination with the EGFR tyrosine kinase inhibitor, the PD-1/-L1 immune checkpoint pathway inhibitor, and/or the molecular-targeted agent for treatment of EGFR gene mutation-positive lung cancer.

Abstract: The present invention provides a method of determining a lung cancer treatment, the method comprising: measuring an amount of KL-6 in a sample of body fluid from a subject, and determining the treatment based on the amount of KL-6 measured, and a method of determining the effectiveness of an agent for treatment of lung cancer on a subject, the method comprising: measuring an amount of KL-6 in a sample of body fluid from the subject, determining the effectiveness of an EGFR inhibitor on the subject should the EGFR inhibitor be administered as the agent for treatment of lung cancer, based on the amount of KL-6 measured.