Five-Year Trends in Biomarker Testing and Targeted Therapy for NSCLC: A Patient-Initiated Nationwide Survey in Japan

Although multigene testing for advanced non-small cell lung cancer (NSCLC) is reimbursed in Japan, optimizing its real-world clinical impact remains challenging. This study updates nationwide testing trends and evaluates the treatment gap between diagnostic results and first-line therapeutic interventions. We conducted a retrospective cohort study using the Diagnosis Procedure Combination database (April 2019 to May 2024). The analysis included 24,047 patients with Stage IV NSCLC across 300 hospitals who underwent diagnostic lung biopsies. Comprehensive multigene testing shifted significantly; testing for ≥ 5 genes rose sharply from late 2021, followed by a marked increase in 6-7 gene testing from mid-2023. Testing for rare drivers (MET, RET, KRAS, HER2) increased substantially. However, approximately 30% of patients remained untested regardless of region or age. While the proportion of patients receiving first-line targeted therapy plateaued at just under 30%, the use of targeted therapies for rare drivers showed a steady increase. In conclusion, multigene testing has rapidly replaced single-gene testing in Japan, narrowing the diagnostic gap for rare oncogenic drivers. Nevertheless, the persistent 30% untested rate emphasizes the need for better shared decision-making to ensure all patients receive comprehensive biomarker evaluation.