Savolitinib monotherapy exerted significant benefit in a non-small cell lung cancer patient with osimertinib resistance harboring primary EGFR L858R mutation and MET amplification: a case report.

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) have significantly improved response in all stages of patients with EGFR positive mutations in nonsmall cell lung cancer. However, the primary resistance mechanism of EGFR-TKIs has not been thoroughly revealed. Here, we described a case of a 64-year-old male with lung adenocarcinoma presented primary resistance on osimertinib combined with bevacizumab and platinum-based chemotherapy, next-generation sequencing revealed EGFR exon 21 L858R mutation and MET gene amplification. Afterward, savolitinib monotherapy was started until now, and the treatment was temporarily successful, the last follow-up clinical evaluation was near complete response, the progression-free survival has over 7 months. Our case highlights that EGFR-TKIs may be not the optimal choice for lung adenocarcinoma with primary EGFR -sensitive mutation with MET amplification simultaneously, whereas MET inhibitor alone may be an effective treatment option. In clinical practice, we should fully consider the possibility of primary resistance in EGFR-TKIs administration.