GUIding Multi-moDal thErapies Against MRD by Liquid Biopsies in Colorectal Cancer - GUIDE.MRD-01-CRC

GUIDE.MRD-01-CRC is a part of WP3 of the overarching GUIDE.MRD project. Each study chair has a local clinical trial protocol where patients are recruited. After the end of recruitment, samples will be analyzed under the GUIDE.MRD consortium.

The overall aim of GUIDE.MRD is to investigate the clinical utility of ctDNA analysis to predict and guide the choice of multi-modal therapies prospectively. The fundamental steps towards this aim are assessment and benchmarking of the many available ctDNA diagnostics to identify the best-suited tests for clinical application. Clinical samples will be used to benchmark ctDNA diagnostics and assess their true clinical performance. The samples should reflect clinical situations where the ctDNA diagnostics are particularly useful, such as post-operatively, post-adjuvant, during chemotherapy, and longitudinally during post-treatment surveillance. In these situations, ctDNA diagnostics could be used to either monitor treatment response (in case of MRD after surgery) or to identify relapse at an early time point. Based on ctDNA information, medical treatment could be changed, or radiology could be used to reveal the location of residual disease.

The rationale for the observational clinical study GUIDE.MRD-01-CRC is to prospectively collect the clinical samples needed to enable assessment of the performance of ctDNA diagnostics in the setting of colorectal cancer (CRC). There are two main scenarios where ctDNA diagnostic is useful in CRC:

Stage III CRC (locally advanced, non-metastasized disease): This patient group is particularly relevant because adjuvant therapy is recommended for all stage III patients, due to their high recurrence risk, ~25%. Nevertheless, most patients do not recur, and most of these do not need therapy at all, because they were already cured by surgery alone, which leads to substantial overtreatment. Furthermore, the 25% of patients who recur despite both surgery and adjuvant therapy, probably could benefit from further multimodal therapies. The challenge is, however, that currently there is no marker in clinical use that can identify those patients with residual disease and need for therapy. Circulating tumor DNA is potentially such a marker. However, currently, it is unknown, which, if any, of the many different ctDNA diagnostics developed in recent years have the required performance to provide clinical utility in the management of stage III CRC. This clinical dilemma will be addressed with the first cohort of GUIDE.MRD-01-CRC.

Metastatic CRC with isolated liver metastases. Metastatic CRC with liver metastases is a unique tumor type in that surgical resection or complete ablation of the metastases, is the standard of care. In virtually all other tumor types, resection of liver metastases is considered only within clinical trials or in exceptional clinical circumstances. In contrast, resection, or ablation of colorectal cancer liver metastases (CRLM) are routinely performed with curative intention, and the overall 5-year survival is around 50%. Most relapses present within three years after operative intervention. The clinical benefit of adjuvant chemotherapy is currently a matter of debate, due to limited data from randomized controlled trials and recent results that indicate inferior overall survival (OS) in patients who received adjuvant therapy (JCOG0603). Based on these and earlier data (EORTC Trial 40983) that failed to show an OS benefit of adjuvant therapy after CRLM resection, it can be assumed that most patients are treated unnecessarily with chemotherapy, and those patients that could receive targeted agents are missed. No histological or clinical markers are available to guide decisions on adjuvant treatment. In this setting, ctDNA could be valuable to guide decisions on adjuvant chemotherapy (yes/no), the addition of biologicals such as anti-VEGF and anti-EGFR agents, targeted therapies in the case of BRAF mutations, or the presence of microsatellite instability (MSI), for example.