Acquired L718V/TP53 co-mutation and discordant molecular pattern between plasmatic and cerebrospinal fluid in a bone and meningeal metastatic L858R+ non-small cell lung cancer: a case report.

ABSTRACT

Background: Osimertinib is approved in first line metastatic epidermal growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC). Acquired EGFR L718V mutation is a rare mechanism of resistance towards osimertinib in L858R+ NSCLC with potential sensibility to afatinib. This case reported an acquired EGFR L718V/TP53 V727M resistance co-mutation to osimertinib with discordant molecular pattern between plasmatic and cerebral fluid in a leptomeningeal and bone metastatic EGFR L858R mutant NSCLC. Case Description A 52-year-old female, diagnosed with a bone metastatic EGFR L858R-mutated NSCLC, was treated with osimertinib as second line treatment for a leptomeningeal progression. She developed an acquired EGFR L718V/TP53 V272M resistance co-mutation after seventeen months of treatment. Discordant molecular status was observed between plasmatic (L718V+/TP53+/L858R+) and cerebrospinal fluid (CSF) (L718V-/TP53+/L858R+). Afatinib as third line did not prevent neurological progression. Conclusions: Acquired EGFR L718V mutation mediate a rare mechanism of resistance to osimertinib. Some cases reported sensibility to afatinib in patients with EGFR L718V mutation. In this described case, afatinib had no efficacy against neurological progression. This could be explained by the absence of EGFR L718V mutation in CSF tumor cells and concomitant TP53 V272M mutation as negative survival prognostic. Identify resistance mechanisms against osimertinib and develop specific therapeutic approaches remain a challenge in clinical routine.