The goal of this prospective interventional biomarker development and validation study is to determine whether circulating tumour DNA (ctDNA) can be detected in patients with large pre-neoplastic colorectal lesions undergoing endoscopic resection and whether ctDNA can be used to identify local recurrence after resection.
The main questions it aims to answer are:
* Can advanced colorectal laterally spreading tumours (LSTs) shed detectable ctDNA into the bloodstream before endoscopic resection? * Can ctDNA measured at the first surveillance colonoscopy detect or predict local recurrence after endoscopic resection?
Participants will:
* Provide a blood sample before their planned endoscopic resection procedure for ctDNA analysis. * Undergo standard endoscopic resection of their colorectal lesion. * Allow collection and molecular analysis of tissue samples obtained from the resected lesion. * Allow researchers to collect clinical, endoscopic, pathological, and molecular data from their medical records for research purposes.
The study does not alter the standard clinical management, resection technique, or surveillance schedule. The only study-specific procedures are blood sample collections performed during routine intravenous catheter placement for the participant's endoscopic procedures.
Age ≥ 18 years.
Referred for resection of a large (≥ 10 mm) colorectal laterally spreading tumour (LST).
Lesion judged amenable to endoscopic resection by the treating endoscopist.
Able to provide written informed consent.
Known concurrent or prior colorectal cancer, or another active malignancy that could contribute circulating tumour DNA.
Lesion < 10 mm.
Inability to provide informed consent.
Single group
Blood Collection for ctDNA Analysis
Diagnostic testBlood samples will be collected before endoscopic resection for circulating tumour DNA (ctDNA) analysis. Results will be correlated with tumour tissue sequencing findings and surveillance colonoscopy outcomes.
Pre-resection ctDNA Detection Rate
Detection of circulating tumour DNA (ctDNA) in the pre-resection plasma sample using a tumour-informed assay. A positive result is defined according to the prespecified threshold for detected tumour-specific variants. The primary outcome is the proportion of evaluable lesions with detectable ctDNA prior to endoscopic resection.
Local recurrence according to pre-resection ctDNA status
Proportion of patients with local recurrence at the first surveillance colonoscopy stratified by pre-resection ctDNA status (positive vs negative).
Quantitative pre-resection ctDNA signal
Distribution of quantitative plasma ctDNA measurements (variant allele fraction and/or tumor molecules per mL) in evaluable lesions.
ctDNA detection rate by lesion characteristics
Pre-resection ctDNA detection rate according to lesion size, histology, dysplasia grade, morphology, and location.
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