This study will develop an assay to predict disease recurrence in patients with stage II/III CRC after receiving adjuvant chemotherapy, using genome-wide DNA methylation.

Adjuvant chemotherapy (ACT) is the standard clinical care for patients with stage III or high-risk stage II colorectal cancer (CRC) after curative-intent resection. Nonetheless, more than 30% of patients experience CRC recurrence. Accurate prediction of recurrence risk in stage II/III CRC patients who undergo ACT is crucial for determining the necessity and duration of ACT, as well as for tailoring novel treatment strategies for these patients.

This study will comprise three phases

1. A systematic and comprehensive CpG methylation-based epigenetic biomarker discovery phase to identify the differentially methylated CpG sites associated with recurrence-free survival (RFS) < 5 years and > 5 years. In this phase, LASSO-based machine learning algorithms will be used to optimize the biomarker candidates.
2. A tissue-based clinical assay development phase by quantitative pyrosequencing
3. An independent validation phase.

At completion, this study will validate a tissue-based assay to predict the development of recurrence after the completion of chemotherapy in patients with stage III and II CRC

Inclusion Criteria:

• Stage II (high-risk) or III colorectal cancer (TNM classification, 8th edition).
• Received standard diagnostic, staging, and therapeutic procedures as per local guidelines
• Received stage-specific curative-intent resection followed by adjuvant chemotherapy.
• Confirmed cancer-free survivorship confirmed at the time of study inclusion.

Exclusion Criteria:

• Lack of written informed consent.
• Development of recurrence in the first 6 months following adjuvant chemotherapy completion.
• Hereditary colorectal cancer syndromes (identified through genetic testing)
• Inflammatory bowel diseases

Two independent cohorts of colorectal cancer survivors (high-risk stage II and stage III), who received curative-intent surgery and adjuvant chemotherapy

Data collected for the study will be made available to others, including de-identified participant data, at publication, via a signed data access agreement and at the discretion of the investigators' approval of the proposed use of such data.