Circulating tumor DNA (ctDNA) detection has shown potential in predicting treatment outcomes for patients with colorectal cancer, according to data presented at the ASCO Gastrointestinal Cancers Symposium. The study found that ctDNA-based detection of molecular residual disease (MRD) and ctDNA dynamics in response to adjuvant chemotherapy are highly prognostic of patient outcomes.
The research involved an updated analysis from the observational GALAXY study, focusing on patients with radically resected stage II to stage IV colorectal cancer. The study used a personalized, tumor-informed assay to detect and quantify ctDNA in serial plasma samples collected at various intervals post-surgery until disease recurrence. CT scans of the chest, abdomen, and pelvic regions were also conducted every 6 months.
The primary endpoint of the study was disease-free survival (DFS), defined as the time between the date of surgery and the date of detection of relapse or death due to any cause. Out of 5,781 patients enrolled in the GALAXY study, 2,998 met the inclusion criteria for data analysis.
Key findings include:
- Patients who tested ctDNA-positive during the MRD window had significantly inferior DFS compared to ctDNA-negative patients.
- In the MRD-positive subgroup, landmark analysis showed that patients who remained ctDNA-positive had a higher likelihood of disease recurrence compared to those with ctDNA clearance.
- Patients with sustained ctDNA clearance had better outcomes compared to those with transient clearance.
- A significant DFS improvement was observed in patients who experienced a 50% or greater decrease in ctDNA levels at 6 months post-adjuvant therapy.
These results suggest that ctDNA detection post-surgery and ctDNA dynamics during surveillance are significantly associated with DFS. The study provides valuable markers for oncologists in treating colorectal cancer patients and highlights the importance of ctDNA-guided adjuvant strategies, which will be further established by ongoing randomized interventional trials.