MA08.01 A Highly Sensitive Next-Generation Sequencing Platform for Detection of NSCLC EGFR T790M Mutation in Urine and Plasma

Abstract

Non-invasive genotyping of NSCLC patients by circulating tumor (ct)DNA is a promising alternative to tissue biopsies. However, ctDNA EGFR analysis remains challenging in patients with intrathoracic disease, with a reported 26-57% T790M mutation detection rate in plasma (Karlovich et al., Clin Cancer Res 2016; Wakelee et al., ASCO 2016). We investigated whether a mutation enrichment NGS could improve mutation detection in plasma and urine from TIGER-X, a phase 1/2 study of rociletinib in patients with EGFR mutation-positive advanced NSCLC. The therascreen (Qiagen) or cobas (Roche) EGFR test was used for EGFR T790M analysis in tumor biopsies. Urine and plasma were analyzed by trovera mutation enrichment NGS assay (Trovagene). Of 174 matched tissue, plasma and urine specimens, 145 (83.3%) were T790M+ by central tissue testing, 142 (81.6%) were T790M+ by plasma, and 139 (79.9%) were T790M+ by urine. Urine and plasma combined identified 165 cases (94.8%) as T790M+. Of 25 cases positive by ctDNA but negative/inadequate by tissue, 16 were double-positive in plasma and urine, unlikely to be false positive (Figure 1). T790M detection rate was higher for extrathoracic (n=119) vs intrathoracic (n=55) disease in plasma (87.4% vs 69.1%, p=0.006) but not urine (81.5% vs 76.4%, p=0.42). Combination of urine and plasma identified T790M in 92.7% of intrathoracic and 95.8% of extrathoracic cases (p=0.47). In T790M+ patients, objective response rate was similar whether T790M mutation was identified by tissue, plasma or urine: 37.4%, 33.1% and 36.6%, respectively. 4 of 9 patients T790M+ by urine but negative by tissue responded, and 2 of 8 patients T790M+ by plasma but negative by tissue responded. Mutation enrichment NGS testing by urine and plasma combined identified 94.8% of T790M+ cases. Combination of urine and plasma may be considered before tissue testing in EGFR TKI resistant NSCLC, including patients without extrathoracic metastases.