Genetic biomarkers from tumor DNA circulating in the bloodstream could indicate the risk for recurrence of colorectal cancer and the efficacy of chemotherapy after surgery. These results could advance the development of noninvasive tests for detection, surveillance, and treatment of cancer.1
“Prior studies, including ones from our group, have shown that this technique is sensitive enough to detect tumor DNA fragments in patients with advanced cancer,” explained Bert Vogelstein, MD, co-director of the Ludwig Center at Johns Hopkins University, Baltimore, Maryland, and study leader.
“But this new study gets us one major step closer to the real goal, because it suggests that it can detect residual disease in early stage patients well before conventional clinical or radiologic criteria can.”
These results could help colorectal oncologists determine whether stage 2 colon cancer should be treated with adjuvant chemotherapy. Current methods for deciding whether to administer adjuvant chemotherapy, such as microscopic examination of the tumor’s appearance, are imprecise, frequently prompting physicians to advise more cautious treatment.
Up to 40% of patients with stage 2 disease undergo adjuvant chemotherapy even though only a small proportion will experience disease relapse.
“The routine procedure is to give 6 months of chemotherapy, but we don’t have any way of knowing if the treatment is effective,” said Jeanne Tie, MD, a Ludwig investigator at the Walter and Eliza Hall Institute of Medical Research in Victoria, Australia, and first author.
Tumors frequently slough DNA into the bloodstream when they die, and mutations in circulating tumor DNA (ctDNA) can function as specific cancer biomarkers. Researchers collected tumor samples from 230 patients with stage 2 colorectal cancer. They analyzed the tumors’ DNA and designed personalized tests to target each patient’s specific genetic mutations.
Researchers then applied these personalized tests to blood samples collected 4 to 10 weeks after surgery. Researchers discovered ctDNA in 20 patients. From this group, 80% experienced relapsed disease within approximately 2 years. Only 10% of the patients who tested negative for ctDNA experienced relapse.
This study then examined whether ctDNA could assess the effectiveness of chemotherapy. Of the patients who tested positive for ctDNA, 6 received chemotherapy. In 2 patients, ctDNA disappeared following chemotherapy, suggesting chemotherapy was effective in these patients. Larger sample sizes are needed to confirm these results.
1. Tie J, Wang Y, Tomasetti C, et al. Circulating tumor DNA analysis detects minimal residual disease and predicts recurrence in patients with stage II colon cancer. Sci Transl Med. 2016 Jul 6. doi: 10.1126/scitranslmed.aaf6219. [Epub ahead of print]