Comparative assessment of NOIR-SS and ddPCR for ctDNA detection of EGFR L858R mutations in advanced L858R-positive lung adenocarcinomas

Longitudinal Monitoring of Circulating Tumor DNA From Plasma in Patients With Curative Resected Stages I to IIIA EGFR-Mutant Non-Small Cell Lung Cancer

INTRODUCTION

For patients with early stage EGFR-mutant-positive (EGFR-M+) NSCLC, curative surgery followed by adjuvant chemotherapy is considered the standard of care. This study evaluated the feasibility and efficacy of longitudinal monitoring of circulating tumor DNA (ctDNA) as a valuable biomarker for early detection of minimal residual disease (MRD) and provides identification of the group at high risk for recurrence in resected stages I to IIIA EGFR-M+ NSCLC.

METHODS

Between August 2015 and October 2017, a total of 278 patients with curative resected, stages I to IIIA (American Joint Committee on Cancer seventh version) common EGFR-M+ NSCLC were analyzed. Radiological follow-up was accompanied with longitudinal monitoring of ctDNA using a droplet-digital polymerase chain reaction from baseline (preoperative), 4 weeks after curative surgery, and follow-up per protocol until 5 years. The primary outcomes were disease-free survival (DFS) according to the status of ctDNA positivity at landmark points and the sensitivity of longitudinal monitoring of ctDNA.

RESULTS

Among 278 patients, preoperative baseline ctDNA was detected in 67 (24%) patients: 23% (stage IA), 18% (IB), 18% (IIA), 50% (IIB), and 42% (IIIA) (p = 0.06). Of patients with baseline ctDNA, 76% (51 of 67) had clearance at 4 weeks after surgery (postoperative). Patients were classified into the following three groups; group A, baseline ctDNA negative (n = 211) versus group B, baseline ctDNA positive but postoperative MRD negative (n = 51) versus group C, baseline ctDNA positive and postoperative MRD positive (n = 16). The 3-year DFS rate was significantly different among the three groups (84% for group A, 78% for group B, and 50% for group C, p = 0.02). After adjusting for clinicopathologic variables, ctDNA still remains an independent risk factor for DFS along with stage (p < 0.001) and micropapillary subtype (p = 0.02). With longitudinal monitoring of ctDNA, MRD was detected before radiological recurrence in 69% of patients with exon 19 deletion and in 20% with L858R mutation.

CONCLUSIONS

These results suggest that patients with baseline ctDNA-positive or MRD-positive status were associated with poor DFS in curative resected stages I to IIIA EGFR-M+ NSCLC and that longitudinal monitoring of ctDNA, a noninvasive method, might be useful to detect early recurrence before radiological recurrence.

Droplet magnetic-controlled microfluidic chip integrated nucleic acid extraction and amplification for the detection of pathogens and tumor mutation sites

Traditional nucleic acid extraction and detection is based on open operation, which may cause cross-contamination and aerosol formation. This study developed a droplet magnetic-controlled microfluidic chip integrated nucleic acid extraction, purification and amplification. The reagent is sealed in oil to form a droplet, and the nucleic acid is extracted and purified by controlling the movement of the magnetic beads (MBs) through a permanent magnet, ensuring a closed environment. This chip can automatically extract nucleic acid from multiple samples within 20 min, and can be directly placed in the in situ amplification instrument for amplification without further transfer of nucleic acid, characterized by simple, fast, time-saving and labor-saving. The results showed that the chip was able to detect <10 copies/test SARS-CoV-2 RNA, and EGFR exon 21 L858R mutations were detected in H1975 cells as low as 4 cells. In addition, on the basis of the droplet magnetic-controlled microfluidic chip, we further developed a multi-target detection chip, which used MBs to divide the nucleic acid of the sample into three parts. And the macrolides resistance mutations A2063G and A2064G, and the P1 gene of mycoplasma pneumoniae (MP) were successfully detected in clinical samples by the multi-target detection chip, providing the possibility for future application in the detection of multiple pathogens.

Fragment size and dynamics of EGFR-mutated tumor-derived DNA provide prognostic information regarding EGFR-TKI efficacy in patients with EGFR-mutated NSCLC

Circulating tumor DNA (ctDNA)-based next-generation sequencing (NGS) is a complementary and alternative test to tissue-based NGS. We performed NGS analysis of ctDNA samples collected from patients with EGFR-mutated non-small cell lung cancer (NSCLC) who received osimertinib; the samples were collected after second-line treatment, before osimertinib treatment, one week and one month after osimertinib treatment, and at the time of resistance formation. We examinedthe correlation with osimertinib efficacy. From January to December 2018, 34 patients with EGFR-mutated NSCLC harboring EGFR T790M mutations were enrolled, and a total of 132 peripheral blood samples were collected. The fragment sizes of EGFR-mutated ctDNAs were significantly shorter than that of their corresponding normal fragments. Osimertinib treatment of patients with shorter EGFR-mutated ctDNA fragments resulted in shorter progression-free survival (PFS). The disappearance time of EGFR-mutated fragment fractions and clonal evolution patterns (new driver mutation group, additional mutation group vs. attenuation group) were each associated with the PFS achieved with osimertinib treatment; however,multivariate analysis revealed that only shorter EGFR-mutated ctDNA fragments were associated with the PFS resulting from osimertinib treatment. EGFR-mutated ctDNA fragment size, time of disappearance of these fragments, and clonal evolution pattern were related to the effects of osimertinib. In particular, short EGFR-mutated ctDNA fragmentation may be closely related to osimertinib efficacy prediction.