A case of different gene mutations in primary and metastatic lesions after EGFR-TKI treatment of lung cancer.

BACKGROUND

It remains controversial whether patients with EGFR-mutant lung adenocarcinoma should stop using epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) after progression during treatment.

CASE REPORT: We report a 35-year-old man with poorly differentiated adenocarcinoma of the left upper lobe and an exon 19 deletion (Ex19Del) mutation found by large-panel next-generation sequencing. The patient underwent video-assisted thoracoscopic surgery 12 months after oral administration of icotinib 125 mg tid, and the left upper lobe and surrounding lymph nodes were removed. Postoperative pathology supported a diagnosis of left upper lobe adenocarcinoma and subcarinal (1/2), main pulmonary artery window (1/2), and left hilar (1/2) lymph node metastases. The EGFR mutations in the residual lesions had disappeared, and Ex19Del mutations were still visible in the mediastinal lymph node metastasis.

CONCLUSION

Spatial heterogeneity of the resistance mechanism may explain why patients who continue to receive EGFR-TKIs in combination with local therapies (e.g., radiotherapy) for progressing lesions may benefit even after progression during EGFR-TKI therapy. The loss of the EGFR mutation allele as a putative resistance mechanism requires additional preclinical and clinical confirmation.