Abstract 327: The impact of PIK3CA/PTEN/AKT1 genes in advanced NSCLC patients with acquired EGFR-TKI resistance and clinical response to EGFR-TKI plus everolimus combination therapy

Abstract

Abstract Background EGFR-TKIs have shown remarkable effect in non-small cell lung cancer (NSCLC) patients with sensitive EGFR mutations. Nevertheless, several mechanisms including activation of PI3K/AKT/mTOR pathway have been proved to generate acquired assistance to EGFR-TKIs. In this study, we investigated the genomic characteristics of PI3K pathway in NSCLC patients with acquired resistance to EGFR-TKIs and whether both targeting EGFR and mTOR could reverse resistance. Methods A total of 605 NSCLC cases who received prior TKI treatment were reviewed, in which 328 patients harboring EGFR-mutants were confirmed to have progressed on one or more TKI and finally enrolled. FFPE tumor or blood samples were collected at the onset of TKI resistance for NGS based panel assay (PIK3CA/PTEN/AKT1 genes and NSCLC driver genes are included). Six patients with co-mutations in EGFR and PI3K pathway who had been heavily treated and progressed on EGFR-TKI received EGFR-TKI plus mTOR inhibitor everolimus combination therapy. Results In a total of 328 patients, 294 (89.6%) of the patients were adenocarcinomas, 4(12.2%) were small cell lung cancer, while the rest were squamous carcinoma or NSCLC not otherwise specified (30, 9.2%). Forty nine (14.9%) patients with TKI resistant have genomic alterations in PI3K pathway. PIK3CA, PTEN and AKT1variations were detected in 31(9.5%), 18(5.5%) and 3(0.9%) of patients respectively. Three patients had both PIK3CA and PTEN mutations and one patient had co-mutation of PIK3CA/PTEN/AKT1. PIK3CA hotspot mutations of E545, H1047 and E542 accounted for 60.5% of PIK3CA mutations. Six patients were treated with everolimus (5mg) plus EGFR-TKI (2 patients with gefitinib, 250mg; 1 patient with afatinib, 30mg; 3 patients with osimertinib 80mg, daily) combination therapy. One (1/6, 16.7%) patient achieved partial response and the rest (5/6, 83.3%) achieved stable disease. The most common adverse events were dental ulcer (6/6), rash (2/6), pruritis (1/6) and diarrhea (1/6). One patient withdrew combination treatment due to grade 3 dental ulcer. Conclusions Our study revealed that PI3K pathway was activated in approximately 15% of EGFR-TKI resistant patients. Combination therapy of EGFR-TKIs and everolimus revealed limited antitumor activity in EGFR-TKI resistant NSCLC patients with dysregulation of PI3K pathway. Citation Format: Wenfeng Fang, Yihua Huang, Jiadi Gan, Yunpeng Yang, Yifen Wu, Jingbin Huang, Zhiyong Xu, Wenjing Wang, Li Zhang. The impact of PIK3CA/PTEN/AKT1 genes in advanced NSCLC patients with acquired EGFR-TKI resistance and clinical response to EGFR-TKI plus everolimus combination therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 327.