...for LUAD patients harboring EGFR mutation (N = 64), low ARID1A expression still predicted a favorable response to immunotherapy, as represented by a higher ESTIMATE score (P = 0.0372), immune score (P = 0.0072) and IPS score....EGFR-mutant LUAD patients with low ARID1A expression had better progression-free survival (PFS) than those with high ARID1A expression (5.63 months versus 1.59 months, P = 0.0458)....The ARID1A low expression group had a higher disease control rate (DCR) than the high expression group (80% versus 25%) in the best response to ICI treatment....Low ARID1A expression is associated with infiltrating immune cell accumulation and a better response to ICI treatment in EGFR-mutant LUAD patients.