A randomized phase III study optimizing adjuvant osimertinib for resected EGFR -mutant stage II–III non-squamous non-small cell lung cancer: OASIS trial (JACTOP-01)

The OASIS trial [Japan Cancer Treatment Optimization group (JACTOP)-01] is a multicenter, randomized, open-label, phase III study optimizing adjuvant osimertinib therapy for patients with completely resected, epidermal growth factor receptor (EGFR)-mutated (exon 19 deletion or L858R) stage II–III non-squamous non-small cell lung cancer. Based on the ADAURA trial, the standard adjuvant dose of osimertinib is 80 mg/day, which often causes significant adverse events and financial toxicity. This trial evaluates the non-inferiority of a reduced dose of 40 mg/day of osimertinib compared to the standard 80 mg/day. A total of 420 patients will be randomized (1:1) to receive either osimertinib 80 or 40 mg/day orally for 3 years. The primary endpoint is disease-free survival. Secondary endpoints include overall survival, central nervous system disease-free survival, safety, and quality of life. If non-inferiority is confirmed, osimertinib 40 mg/day will establish a new optimal adjuvant strategy, improving patient quality of life and reducing medical economic burdens.