Therefore, combination therapy with EGFR-TKIs and ER inhibitors is considered more effective than EGFR-TKIs alone and the combination of EGFR-TKIs and fulvestrant, an ER antagonist, suppresses the proliferation of NSCLC cells with or without EGFR mutations [41,55]. The gene discussed is ESR1; the disease is non-small cell lung carcinoma.