Harnessing minimal residual disease for precision medicine in locally advanced gastric cancer

Table 1 Key characteristics of polymerase chain reaction-based and next-generation sequencing-based circulating tumor DNA analysis technologies

	ddPCR-based ctDNA-MRD assay	NGS-based ctDNA-MRD assay
Core technical principle	Microdroplet-partitioned single-molecule PCR amplification, absolute quantification of ctDNA mutations based on Poisson distribution[25,26]	Target region capture + high-throughput sequencing, combined with UMI for ctDNA mutation quantification[25,27]
LOD	0.01%-0.1% VAF[26]	0.1%-0.5% VAF (standard depth); < 0.01% VAF (ultra-deep sequencing)[27]
Detectable variant types	Only pre-designed known SNV and insertions/deletions (indel)[25,26]	Simultaneous detection of SNV, indel, CNV, and gene fusions[25,27]
Detection turnaround time	1-3 working days	5-7 working days
Single sample detection cost	Low (approximately 100-300 USD per sample)	Medium-high (approximately 500-1500 USD per sample)
Core advantages	Simple operation, low cost, short detection cycle, high absolute quantification accuracy[25,26]	Covers multi-gene and multi-variant types, tracks tumor heterogeneity, adapts to personalized panel design[25,27]
Core limitations	Only detects known mutations, cannot cover tumor heterogeneity, low throughput[25,26]	Long detection cycle, high cost, complex data analysis, lower sensitivity than ddPCR at standard sequencing depth[25,27]

ddPCR: Droplet digital polymerase chain reaction; ctDNA: Circulating tumor DNA; MRD: Minimal residual disease; NGS: Next-generation sequencing; PCR: Polymerase chain reaction; UMI: Unique molecular identifier; LOD: Limit of detection; VAF: Variant allele frequency; SNV: Single nucleotide variants; Indel: Insertion and deletion; CNV: Copy number variations.

Table 2 Key studies on circulating tumor DNA assessment of minimal residual disease for recurrence prediction and prognosis assessment in locally advanced or resectable gastric cancer

Ref.	Population and design	Assay and sampling	Key result/effect size	Critical interpretation/limitations
Yang et al[11]	46 stage I-III GC patients after curative-intent resection; prospective cohort	Targeted deep sequencing; preoperative, postoperative, and serial follow-up samples	Postoperative ctDNA positivity was associated with high recurrence risk; molecular relapse preceded radiological recurrence by a median of about 6 months	Proof-of-concept evidence for prognosis, but small cohort and limited power; not sufficient to establish ctDNA-guided therapy
Leal et al[40]	Resectable GC patients from the CRITICS phase III trial; translational analysis	Ultrasensitive targeted sequencing with leukocyte filtration; after preoperative treatment and postoperatively; follow-up NR in this minireview	ctDNA detection at key perioperative time points predicted recurrence	Analytically rigorous workflow, but timing and assay differ from other studies; clinical actionability remains untested
Lan et al[41]	428 GC patients; large-scale clinical study	Dynamic postoperative ctDNA monitoring; detailed platform not uniformly reported in this minireview	Persistent postoperative ctDNA elevation was more closely associated with recurrence than CEA; preoperative ctDNA was not clearly correlated with recurrence	Highlights that baseline ctDNA and postoperative MRD are not interchangeable; thresholds still need standardization
Min et al[42]	GC patients included in multiple studies; meta-analysis	Mixed ctDNA assays, sampling time points, and follow-up schedules	ctDNA was associated with prognosis; post-chemotherapy ctDNA level correlated with DFS	Broader evidence base, but pooled interpretation is limited by heterogeneity in platforms and thresholds
Wu et al[43]	LAGC patients; clinical detection study	ctDNA mutation-burden analysis before and after treatment; follow-up NR in this minireview	Higher ctDNA mutational burden correlated with shorter OS; reduced mutational frequency after treatment was associated with better PFS/OS	Suggests value of quantitative burden, but reproducibility and cutoff definitions require validation

GC: Gastric cancer; ctDNA: Circulating tumor DNA; NR: Not reported or not consistently extractable from the cited report; CEA: Carcinoembryonic antigen; MRD: Minimal residual disease; DFS: Disease-free survival; LAGC: Locally advanced gastric cancer; OS: Overall survival; PFS: Progression-free survival.