We found that patients with HER2-mutant lung cancers had a PFS of 5.1 months that was similar with KRAS-mutant (5.0 months, p = 0.971) lung cancers, and numerically shorter than EGFR-mutant (6.5 months, p = 0.247) and significantly shorter than ALK/ROS1-rearranged (9.2 months, p = 0.004) lung cancers, showing that HER2-mutant lung cancer patients may have poor outcomes with chemotherapy, which strengthen the importance of developing HER2-targeted drugs in this population. This evidence concerns the gene EGFR and lung cancer.