The ability to optimize adjuvant chemotherapy recommendations for patients with resected colorectal cancer (CRC) has been historically limited by the use of clinicopathologic characteristics, which imperfectly prognosticate the risk for recurrence. In patients with stage II CRC, variation exists among oncologists, in the absence of a biomarker with demonstrated survival benefit, in the decision to administer adjuvant chemotherapy.1 One approach to identifying patients with resected CRC at higher risk of recurrence that has shown great promise involves the postoperative detection of circulating tumor DNA (ctDNA). Released into the bloodstream from tumor cells predominantly by apoptosis,2 tumor-specific alterations can be identified at variant allele frequencies of 0.1% or lower.3,4 Such a high sensitivity for these ctDNA assays permits the detection of microscopic foci of residual tumor cells that cannot be visualized radiographically. In previous case series of patients with resected CRC,3-5 the presence of ctDNA after surgical resection starkly identified patients with CRC who were likely to relapse, and ctDNA has outperformed traditional risk factors used by oncologists when considering adjuvant chemotherapy.5
Morris V, Dasari A, Kopetz S. Can Circulating Tumor DNA in Early-Stage Colorectal Cancer Be More Than a Prognostic Biomarker? JAMA Oncol. 2019;5(8):1101–1103. doi:10.1001/jamaoncol.2019.0503
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