DANISH.MRD: Danish Assessment of Minimal Residual Disease by Liquid Biopsies

Colorectal cancer (CRC) is the third most common cancer worldwide. Approximately 75% of patients initially present with potentially curable disease, but despite curatively intended treatment up to 25 % of them experience a relapse of the disease. Upon diagnosis, survival of CRC can be improved by offering adjuvant chemotherapy to patients with a high risk of recurrence, or by early detection of recurrence enabling early intervention which improves patient survival significantly. To achieve this, it is essential to have sensitive and specific tools for correctly identifying patients with a high risk of recurrence and the need for adjuvant therapy, and for early detection of recurrence facilitating early intervention. Non-invasive analysis of circulating tumor DNA (ctDNA) is an emerging tool that has this potential.

Objectives

The overall objective of the study is to confirm that ctDNA detected after intended curative treatment for CRC is a marker of residual disease and risk of recurrence and is applicable in clinical practice.

Primary objectives

P1: To determine the prognostic value of a patient's ctDNA status and compare it with other known prognostic factors. Specifically, the aim is to determine the association between 3-year disease-free survival (DFS) and ctDNA detection status immediately after

1. curative-intended surgery and 2) adjuvant chemotherapy.

P2: To identify a cohort of UICC stage III CRC patients with planned adjuvant chemotherapy. These patients will be offered enrollment in the DANISH.MRD part II (Secondary objective 1 (S1)), and will further be included in a European collaboration named GUIDE.MR-01-CRC, funded by the European Union via the Innovative Health Initiative.

Secondary objectives

S1: To technically assess, compare, and rank commercial ctDNA diagnostics and evaluate their performance after intended-curative CRC treatment (postoperatively and post adjuvant chemotherapy) to identify the best-performing method at each time point.

S2: To assess the effect of standard-of-care adjuvant chemotherapy on the level of ctDNA. Especially, for patients with ctDNA detected after surgery, the aim is to measure and compare the ctDNA levels in plasma samples drawn before and after adjuvant chemotherapy. Further, the change in ctDNA level will be correlated to the oncological outcomes (time to clinical recurrence, disease-free survival, and overall survival).

S3: To investigate if time to Molecular recurrence determined using serial ctDNA analyses in longitudinally collected plasma samples is shorter than time to Clinical recurrence using standard-of-care radiological imaging.

S4: To investigate the correlation between ctDNA analysis results and findings on CT scans. ctDNA analysis will be restricted to blood sampling times that coincide with standard-of-care CT scans (at 12 and 36 months postoperatively). If ctDNA analysis can predict the outcome of the CT scan, the potential is that ctDNA analysis in the future can guide when to perform CT scans.

S5: To investigate the prognostic power of ctDNA at the time point of indeterminate CT scans.

S6: To investigate, if molecular characterization of CRC cancers can stratify patients and predict i.e., treatment response, growth patterns, cancer aggressiveness, clinical outcomes, and whether the tumor sheds ctDNA into the circulation.

Investigational plan

The DANISH.MRD study is logistically divided into two parts, and patients are offered participation in each part separately. The parts are called "DANISH.MRD part I - Surgery", and "DANISH.MRD part II - Surveillance".

In DANISH.MRD part I blood samples are collected before and after surgery. For patients receiving neoadjuvant therapy, a blood sample will also be collected before initiation of this treatment.

In DANISH.MRD part II blood samples are collected immediately after adjuvant chemotherapy and during standard-of-care surveillance.

Patients included in DANISH.MRD part I will help address Primary objective 1 (P1). The subset of the part I patients that are also included in DANISH.MRD part II will help to address the Secondary objectives S1-S6.

Both Part I and Part II DANISH.MRD patients receive standard follow-up care, which includes scheduled visits for up to 5 years following their surgery.

Sample collection for DANISH.MRD part I - Surgery (Objectives P1-2, S1-S5)

• Blood sampling preoperatively and after surgery (between days 20-30, but before initiation of adjuvant chemotherapy)

• Sampling of tissue from the resected specimen

Sample collection in DANISH.MRD part II - Surveillance (objectives S1-S5)

• Blood sampling post-adjuvant chemotherapy (ACT): postACT (14-30 days after the end of ACT), and at months 8, 12, 16, 20, 24, 30 and 36 postoperatively.