EGFR status assessment using reflex testing targeted next-generation sequencing for resected non-squamous non-small cell lung cancer.

EGFR status assessment is mandatory for adjuvant decision-making of resected stage IB-IIIA non-squamous non-small cell lung cancer (NS-NSCLC). It is questionable whether single-gene RT-PCR versus next-generation sequencing (NGS) should be used for this evaluation. Moreover, co-occurring mutations have an impact on tumor behavior and may influence future therapeutic decision-making. We aimed to describe the clinico-pathological and molecular features, as well as the prognostic factors of resected EGFR-mutant NS-NSCLC evaluated with reflex NGS and RT-PCR, so as to compare the results of the two methods. We retrospectively included and collected data from patients with resected EGFR-mutant NS-NSCLC diagnosed in our institution between 2005 and 2024. Additional cases from another center were included. Tumors were analyzed using targeted NGS and RT-PCR. A total of 153 patients were selected. The median follow-up after surgery was 22 months. The positive percent agreement of RT-PCR compared to NGS for the detection of an EGFR mutation was 88%. Common single EGFR mutations (L858R/del19) were observed in 117/153 (77%) cases; 22/153 (14%) and 14/153 (9%) cases had uncommon single and compound EGFR mutations, respectively. 63/153 (41%) patients had a co-occurring mutation, including a TP53 mutation in 43/63 (68%) co-mutated patients. EGFR/TP53-mutant tumors were associated with positive PD-L1 expression compared to EGFR-mutant/TP53-wild-type tumors (62% vs 39%; p = 0.006). Shorter median event-free survival (EFS) in patients with an EGFR exon 18 mutation and those with TP53 exon 7 co-mutation was recorded. The EGFR status should be systematically evaluated using targeted NGS reflex testing for resected NS-NSCLC since future therapeutic decision-making could soon consider integrating the presence of co-occurring mutations.