SAN FRANCISCO — A blood test that measures circulating tumor DNA (ctDNA) can help to identify those patients with resectable colorectal cancer who are most likely to derive the most benefit from adjuvant chemotherapy, suggest results from a Japanese study.
The team used a personalized tumor-informed assay (Signatera bespoke multiplex-PCR NGS assay) to measure molecular residual disease (MRD) 4 weeks after surgery.
Among patients who were ctDNA positive at 4 weeks post-op, those who received adjuvant chemotherapy had significantly longer disease-free survival (DFS) at 6 months compared to patients who didn't receive it.
The adjuvant chemotherapy was able to clear ctDNA in 68% of that subgroup by 24 weeks, noted study author Masahito Kotaka, MD, PhD, from Gastrointestinal Cancer Center, Sano Hospital, Hyogo, Japan
"Even with an extended follow-up time, ctDNA positivity at 4 weeks post-op was significantly associated with inferior disease-free survival," he said.
"Two out of three post-op patients who were positive at 4 weeks recurred, even in stage I or low-risk stage II."
However, he noted that "patients who were 4 weeks post-op and ctDNA negative did not derive significant benefit from adjuvant chemotherapy in high- risk stage II and III."
Overall, the study shows that stratifying postsurgical treatment decisions using the assay can identify patients likely to benefit from adjuvant chemotherapy across all stages of the disease, explained Kotaka.
