Circulation tumor DNA (ctDNA) is small pieces of DNA that are released from dead tumor cells. As the tumor grows rapidly, cells die and be replaced by constantly produced new tumor cells. Those dead cells would break down and release their DNA and other intracellular material into the bloodstream. Hence, assessment of ctDNA content in the blood can effectively indicate cancer growth and micrometastases situation.
A study published in the New England Journal of Medicine evaluated the content of ctDNA in stage II colon cancer patients to direct post-surgical therapy of them. In detail, Jeanne Tie and coworkers enrolled 455 patients with resected histologically confirmed stage II colon and randomly assigned them into two groups (ctDNA guided management and standard management) with a ratio of 2:1 to assess whether a ctDNA-guided approach could reduce the use of adjuvant chemotherapy without compromising recurrence risk. Furthermore, they also inspected outcomes among ctDNA-negative patients and ctDNA-positive patients who received adjuvant chemotherapy to assess the effectiveness of the blood test.
As shown in Figure 1, the recurrence or death occurred in 6% of ctDNA-negative patients and 18% of ctDNA-positive patients. The 3-year recurrence-free survival was 92.5% among ctDNA-negative patients and 86.4% among ctDNA-positive patients with the three-year recurrence rates were 7% (ctDNA-negative) and 14% (ctDNA- positive) respectively.
This study run by Jeanne Tie and colleagues proved that the ctDNA blood test can be a scientifical guide approach for decreasing excessive adjuvant therapy and did not influence the recurrence risk of patients. Besides, they are now exploring the use of ctDNA blood tests in the treatment of other cancer types.
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