A personalized liquid biopsy test that detects circulating tumor DNA (ctDNA) in the blood can help identify colorectal cancer patients who are likely to relapse after surgery, researchers reported at the ASCO Gastrointestinal Cancers Symposium. Around 25% of people with colorectal cancer will relapse, and spotting recurrence earlier can help doctors tailor treatment.
In a study of more than 200 people who underwent surgery for Stage I to III colorectal cancer, the patients’ tumor DNA was sequenced to identify mutations, and a Signatera customized ctDNA test was designed to track tumor-specific mutations in their blood samples over time.
Among 218 people who were tested before starting adjuvant, or post-surgery, chemotherapy, the ctDNA test found that 20 had molecular residual disease (MRD), or evidence of remaining cancer. Within this subgroup, 15 people (75%) relapsed. In contrast, just 14% of the 198 patients who tested MRD negative experienced recurrence. People with detectable ctDNA immediately after surgery had a particularly high risk of recurrence. What’s more, the Signatera test was better at detecting residual disease than a commonly used tumor biomarker test.
“We are able to demonstrate that serial ctDNA testing can detect molecular residual disease a median of eight months ahead of clinical relapse, with significant potential to improve patient care,” says Claus Lindbjerg Andersen, PhD, of Aarhus University in Denmark.