ACTN4 gene amplification is a predictive biomarker for adjuvant chemotherapy with UFT in stage I lung adenocarcinomas

Although adjuvant tegafur/uracil (UFT) is recommended for patients with completely resected stage I non‐small‐cell lung cancer (NSCLC) in Japan, only one‐third of cases has received adjuvant chemotherapy (ADJ) according to real‐world data. Therefore, robust predictive biomarkers for selecting ADJ or observation (OBS) without ADJ are needed. Patients who underwent complete resection of stage I lung adenocarcinoma with or without adjuvant UFT were enrolled. The status of ACTN4 gene amplification was analyzed by FISH. Statistical analyses to determine whether the status of ACTN4 gene amplification affected recurrence‐free survival (RFS) were carried out. Formalin‐fixed, paraffin‐embedded samples from 1136 lung adenocarcinomas were submitted for analysis of ACTN4 gene amplification. Ninety‐nine (8.9%) of 1114 cases were positive for ACTN4 gene amplification. In the subgroup analysis of patients aged 65 years or older, the ADJ group had better RFS than the OBS group in the ACTN4‐positive cohort (hazard ratio [HR], 0.084, 95% confidence interval [CI], 0.009‐0.806; P = .032). The difference in RFS between the ADJ group and the OBS group was not significant in ACTN4‐negative cases (all ages: HR, 1.214; 95% CI, 0.848‐1.738; P = .289). Analyses of ACTN4 gene amplification contributed to the decision regarding postoperative ADJ for stage I lung adenocarcinomas, preventing recurrence, improving the quality of medical care, preventing the unnecessary side‐effects of ADJ, and saving medical costs.