ctDNA and TEP Levels in Colon Cancer

Determination of ctDNA and TEP Levels in Patients With Colon Cancer Receiving Neoadjuvant Systemic Therapy

This interventional cohort study will evaluate circulating tumor DNA (ctDNA) and tumor-educated platelets (TEP) as blood-based biomarkers in adults with stage III colon cancer who are planned to receive neoadjuvant systemic therapy followed by surgical resection.

Treatment will be given according to routine clinical practice and will depend on the biological characteristics of the tumor, including mismatch repair status. Participants will provide additional blood samples at predefined time points before, during, and after treatment and surgery. These samples will be used to analyze ctDNA and TEP and to assess whether changes in these biomarkers are associated with radiological response, pathological response, and disease-free outcomes.

Approximately 80 participants will be enrolled at the Institute of Oncology Ljubljana. Participants will not receive experimental drugs as part of this study.

Study Overview

• Status: Not yet recruiting
• Conditions: Colon Cancer
• Intervention / Treatment: Procedure: Additional Peripheral Venous Blood Sampling for ctDNA and TEP Biomarker Analysis

Detailed Description

This is a prospective interventional longitudinal cohort study of adult patients with histologically confirmed stage III colon adenocarcinoma who are planned to receive neoadjuvant systemic therapy followed by surgical resection with curative intent.

The study will evaluate the dynamics of circulating tumor DNA (ctDNA) and tumor-educated platelets (TEP) during neoadjuvant treatment and follow-up. Neoadjuvant systemic therapy will be selected according to routine clinical practice and tumor biology, including mismatch repair status. Patients with pMMR tumors may receive chemotherapy, while patients with dMMR tumors may receive immunotherapy, according to standard clinical decision-making.

The research intervention consists of additional peripheral venous blood sampling at predefined time points before treatment, during systemic treatment, before surgery, and after surgery. Blood samples will be analyzed for ctDNA and TEP-based biomarkers. Clinical, radiological, pathological, and follow-up data will be collected from routine medical documentation.

The primary objective is to determine whether the presence of ctDNA after completion of neoadjuvant systemic therapy is associated with pathological tumor response, defined as major pathological response (MPR), in patients with stage III colon cancer. Secondary and exploratory objectives include evaluation of the association between ctDNA, TEP profiles, radiological response, recurrence-free outcomes, and disease-free outcomes.

Approximately 80 participants will be enrolled. The study is academic and non-commercial. Participants will not receive experimental drugs as part of this study, and all therapeutic and diagnostic procedures will follow established clinical practice.

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Tanja Mesti, MD; Phone Number: +386 1 5879 287; Email: tmesti@onko-i.si

Study Locations

• Slovenia
  • Ljubljana, Slovenia, 1000
    • Institute of Oncology Ljubljana
    • Contact: Klavdija Korošec; Phone Number: +38631630065; Email: kkorosec@onko-i.si
    • Contact: Tanja Mesti, MD; Phone Number: +386 1 5879 287; Email: tmesti@onko-i.si

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age 18 years or older at the time of enrollment.
• Histologically confirmed adenocarcinoma of the colon.
• Stage III colon cancer, defined according to the applicable TNM classification based on clinical and imaging assessment.
• Confirmed mismatch repair (MMR) status, determined by immunohistochemistry and/or molecular methods.
• Planned neoadjuvant systemic therapy according to MMR status, followed by surgical resection with curative intent.
• ECOG performance status 0-2.
• Ability to understand the study and provide written informed consent.

Exclusion Criteria:

• Stage I, II, or IV colon cancer.
• Concurrent active malignant disease, except adequately treated non-melanoma skin cancer or carcinoma in situ.
• Severe comorbidities or medical conditions that prevent or substantially limit neoadjuvant systemic therapy or surgical resection.
• Known autoimmune disease requiring active immunosuppressive treatment in patients with dMMR tumors.
• Pregnancy or breastfeeding.
• Inability or unwillingness to provide written informed consent.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Biomarker Assessment Cohort; Participants with stage III colon cancer receiving neoadjuvant systemic therapy according to routine clinical practice will undergo additional peripheral venous blood sampling at predefined time points for ctDNA and TEP biomarker analysis.	Procedure: Additional Peripheral Venous Blood Sampling for ctDNA and TEP Biomarker Analysis; Additional peripheral venous blood samples will be collected at predefined time points before treatment, during systemic treatment, before surgery, and after surgery. Samples will be analyzed for circulating tumor DNA (ctDNA) and tumor-educated platelets (TEP).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Participants With Major Pathological Response in the Post-Neoadjuvant ctDNA Assessment	Major pathological response will be assessed by histopathological evaluation of the surgical resection specimen after completion of neoadjuvant systemic therapy. The unit of measure will be the percentage of participants with major pathological response. ctDNA status after completion of neoadjuvant systemic therapy will be used as a pre-specified stratification variable in the statistical analysis.	From completion of neoadjuvant systemic therapy to pathological assessment after surgical resection, approximately 3 to 6 months.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Participants With Objective Radiological Response According to RECIST 1.1	Radiological response will be assessed according to RECIST version 1.1 using routine preoperative imaging. Objective radiological response will include complete response and partial response. The unit of measure will be the percentage of participants with objective radiological response. ctDNA status after completion of neoadjuvant therapy will be used as a pre-specified stratification variable in the statistical analysis.	From baseline to preoperative radiological assessment, approximately 3 to 6 months.
Percentage of Participants Alive and Disease-Free at 12 Months After Surgical Resection	Disease-free status will be assessed using routine clinical, radiological, and follow-up documentation. The outcome will be defined as being alive and without disease recurrence at 12 months after surgical resection. The unit of measure will be the percentage of participants alive and disease-free at 12 months. ctDNA status after completion of neoadjuvant therapy will be used as a pre-specified stratification variable in the statistical analysis.	12 months after surgical resection.
Percentage of Participants With Early Disease Recurrence Within 12 Months After Surgical Resection in the Postoperative ctDNA Assessment	Early disease recurrence will be assessed using routine clinical, radiological, and follow-up documentation. The unit of measure will be the percentage of participants with disease recurrence within 12 months after surgical resection. Postoperative ctDNA status will be used as a pre-specified stratification variable in the statistical analysis.	Up to 12 months after surgical resection.
Percentage of Participants With Early Disease Recurrence Within 12 Months After Surgical Resection in the Postoperative TEP Assessment	Early disease recurrence will be assessed using routine clinical, radiological, and follow-up documentation. The unit of measure will be the percentage of participants with disease recurrence within 12 months after surgical resection. Postoperative tumor-educated platelet status will be used as a pre-specified stratification variable in the statistical analysis.	Up to 12 months after surgical resection.
Percentage of Participants With Major Pathological Response in the Baseline ctDNA Assessment	Major pathological response will be assessed by histopathological evaluation of the surgical resection specimen. The unit of measure will be the percentage of participants with major pathological response. Baseline ctDNA status will be used as a pre-specified stratification variable in the statistical analysis.	From baseline to pathological assessment after surgical resection, approximately 3 to 6 months.
Percentage of Participants With Pathological Complete Response After Surgical Resection	Pathological complete response will be assessed by histopathological evaluation of the surgical resection specimen. The unit of measure will be the percentage of participants with pathological complete response. Baseline ctDNA status will be used as a pre-specified stratification variable in the statistical analysis.	From baseline to pathological assessment after surgical resection, approximately 3 to 6 months.

Collaborators and Investigators

• Sponsor: Institute of Oncology Ljubljana

Study record dates

Study Major Dates

• Study Start (Estimated): August 1, 2026
• Primary Completion (Estimated): June 1, 2028
• Study Completion (Estimated): June 1, 2028

Study Registration Dates

• First Submitted: June 18, 2026
• First Submitted That Met QC Criteria: July 8, 2026
• First Posted (Actual): July 14, 2026

Study Record Updates

• Last Update Posted (Actual): July 14, 2026
• Last Update Submitted That Met QC Criteria: July 8, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: TEP; ctDNA; Circulating Tumor DNA; Neoadjuvant Systemic Therapy; Tumor-Educated Platelets
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Intestinal Diseases; Gastrointestinal Neoplasms; Digestive System Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Colorectal Neoplasms; Intestinal Neoplasms; Colonic Diseases; Colonic Neoplasms; Cell-Free Nucleic Acids; Nucleic Acids; Nucleic Acids, Nucleotides, and Nucleosides; DNA, Neoplasm; DNA; Circulating Tumor DNA
• Other Study ID Numbers: ORI2026-25

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No