Furmonertinib plus pemetrexed in the treatment of EGFR exon 19 deletion lung adenocarcinoma: two case reports

Epidermal growth factor receptor (<i>EGFR</i>) exon 19 deletion (Ex19del) is one of the most prevalent sensitizing mutations in non-small cell lung cancer (NSCLC), particularly in Asian populations. However, management after progression or suboptimal response is unclear. We describe two patients with advanced lung adenocarcinoma harboring <i>EGFR</i> Ex19del who received furmonertinib plus pemetrexed. Case 1 achieved partial response (PR) with substantial tumor shrinkage and a marked decline in carcinoembryonic antigen (CEA) after six cycles; disease remained stable over 19 months of follow-up. Case 2 had suboptimal benefit from first-line osimertinib but attained PR with resolution of pleural effusion after switching to the combination; subsequent computed tomography (CT) confirmed stable disease (SD). Both patients tolerated treatment without severe treatment-related adverse events. These observations suggest that furmonertinib plus pemetrexed may have antitumor activity and acceptable tolerability in <i>EGFR</i> Ex19del lung adenocarcinoma, and may inform personalized approaches following resistance to first-line therapy in <i>EGFR</i>-sensitizing NSCLC.