A phase 2/phase 3 clinical trial investigating the efficacy of using circulating tumor DNA (ctDNA) to guide adjuvant chemotherapy in patients with resected stage II colon cancer has been terminated due to disappointing results. The study, presented at the ASCO Gastrointestinal Cancers Symposium, found that ctDNA did not successfully predict whether these patients would benefit from adjuvant chemotherapy.
The trial involved 635 patients with resected stage II colon cancer who were recommended for active surveillance. They were randomly assigned to receive either standard care or ctDNA assay-directed therapy. In the experimental arm, patients with evidence of ctDNA received 6 months of adjuvant chemotherapy.
Of the first 16 patients with detectable ctDNA, seven were in the control group and nine received chemotherapy. After 6 months, 43% of the control group showed no ctDNA, compared to only 11% in the chemotherapy group. The trial was stopped as the probability value exceeded the prespecified significance level.
The study’s findings question the utility of ctDNA as a surrogate marker to guide the use of adjuvant chemotherapy. While the results were disappointing, experts emphasize the ongoing need to explore the role of ctDNA in cancer treatment. Cathy Eng, MD, from Vanderbilt-Ingram Cancer Center, highlighted that the decision to use adjuvant chemotherapy in stage II colon cancer remains a shared decision-making process and that the role of ctDNA must continue to be investigated.