Limited Sensitivity of Circulating Tumor DNA Detection by Droplet Digital PCR in Non-Metastatic Operable Gastric Cancer Patients

Abstract

This study was designed to monitor circulating tumor DNA (ctDNA) levels during perioperative chemotherapy in patients with non-metastatic gastric adenocarcinoma. Plasma samples were prospectively collected in patients undergoing perioperative chemotherapy for non-metastatic gastric adenocarcinoma (excluding T1N0) prior to the initiation of perioperative chemotherapy, before and after surgery (NCT02220556). In each patient, mutations retrieved by targeted next-generation sequencing (NGS) on tumor samples were then tracked in circulating cell-free DNA from 4 mL of plasma by droplet digital PCR. Thirty-two patients with a diagnosis of non-metastatic gastric adenocarcinoma were included. A trackable mutation was identified in the tumor in 20 patients, seven of whom experienced relapse during follow-up. ctDNA was detectable in four patients (N = 4/19, sensitivity: 21%; 95% confidence interval CI = 8.5–43%, no baseline plasma sample was available for one patient), with a median allelic frequency (MAF) of 1.6% (range: 0.8–2.3%). No patient with available plasma samples (N = 0/18) had detectable ctDNA levels before surgery. After surgery, one of the 13 patients with available plasma samples had a detectable ctDNA level with a low allelic frequency (0.7%); this patient experienced a very short-term distant relapse only 3 months after surgery. No ctDNA was detected after surgery in the other four patients with available plasma samples who experienced a later relapse (median = 14.4, range: 9.3–26 months). ctDNA monitoring during preoperative chemotherapy and after surgery does not appear to be a useful tool in clinical practice for non-metastatic gastric cancer to predict the efficacy of chemotherapy and subsequent relapse, essentially due to the poor sensitivity of ctDNA detection.

White blood cell and cell-free DNA analyses for detection of residual disease in gastric cancer

“…A key challenge of liquid biopsy approaches has been developing methods to detect and characterize small amounts of ctDNA in large populations of cell-free DNA (cfDNA). A variety of studies have focused on changes in ctDNA during the course of therapy, but mostly in the setting of metastatic disease and largely centered on the analysis of a limited number of genomic positions that may only represent a subset of clones of the tumor [20][21][22][23][24][25][26][27][28] . More recent studies have used panels of commonly mutated driver genes to allow detection of multiple driver clones, typically at the time of diagnosis, after surgery, or at disease progression 16,18,27,[29][30][31][32][33][34] .…”

Pathology of HPV-Associated Head and Neck Carcinomas: Recent Data and Perspectives for the Development of Specific Tumor Markers

“…Circulating HPV DNA: A specific Form of ctDNA Numerous applications of ctDNA as diagnostic and predictive/ prognostic marker in oncology are under development (65)(66)(67). In most models, ctDNA is detected via the presence of somatic mutations, but the low rate of target molecules, especially in early stage tumors, implies that their detection can be affected by stochastic sampling leading to a lack of target molecules in some specimens (68), a limitation for clinical applications, (69). In this context, HPV-associated tumors represent a privileged model for the detection of ctDNA.…”

Circulating Tumour DNA to Guide Treatment of Gastrointestinal Malignancies

“…ctDNA could serve as a serological screening test, but the correlation between ctDNA detection and early-stage gastric cancers is unclear. An analysis of 20 patients with non-metastatic gastric cancer demonstrated that only 4 had detectable ctDNA at baseline [40]. The CancerSeek platform, combining ctDNA detection with protein biomarkers, reported improved sensitivity rates of 73 and 70% in non-metastatic gastric and oesophageal cancers, suggesting one strategy to improve detection [8].…”