The effect of epidermal growth factor receptor mutation on adjuvant chemotherapy with tegafur/uracil for patients with completely resected, non-lymph node metastatic non-small cell lung cancer (> 2 cm): a multicenter, retrospective, observational study as exploratory analysis of the CSPOR-LC03 study.

Background: The use of adjuvant osimertinib for epidermal growth factor receptor (EGFR) mutants is expected to expand to earlier stage I in the future, potentially competing with the current standard of care, oral tegafur/uracil (UFT), in Japan. However, the effect of EGFR mutation status on the therapeutic effect of UFT remains unclear. This study was conducted as an exploratory analysis of a retrospective observational study that investigated the real-world data of postoperative adjuvant chemotherapy in Japan (CSPOR-LC03).

Methods: Between 2008 and 2013, 1812 patients with completely resected adenocarcinoma diagnosed as pathologic stage I (T1 > 2 cm, TNM classification, sixth edition) who have maintained organ function, and no history of other cancers were included. The primary endpoint was the 5-year disease-free survival (DFS) rate, and we compared this rate between four groups classified based on the administration of adjuvant UFT and EGFR mutation status.

Results: Of the 933 (51%) patients with EGFR mutations, 394 underwent adjuvant UFT therapy. Of the 879 (49%) patients without EGFR mutations, 393 underwent adjuvant UFT therapy. The 5-year DFS of UFT+/EGFR+ and UFT-/EGFR+ patients were 82.0 and 87.1%, respectively, and those of UFT+/EGFR- and UFT-/EGFR- patients were 80.0 and 86.9%, respectively. DFS was significantly worse in the UFT+ group than in the UFT- group (P = 0.015). Adjuvant UFT therapy was not an independent prognostic factor for DFS, regardless of the EGFR mutation status.

Conclusion: In pathologic stage I (>2 cm) lung adenocarcinomas with EGFR mutation, the survival benefit of adjuvant UFT was not observed.