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Dr. Grothey on the Potential Role of ctDNA as a Marker for Rechallenging Treatment in CRC

Axel Grothey, MD, discusses the potential utility of circulating tumor DNA as a marker for rechallenging patients with treatment in colorectal cancer.

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Axel Grothey, MD, medical oncologist and director of Gastrointestinal Cancer Research at West Cancer Center and Research Institute, discusses the potential utility of circulating tumor DNA (ctDNA) as a marker for rechallenging patients with treatment in colorectal cancer (CRC).

EGFR antibodies are standard options for patients with RAS/RAF wild-type left-sided colon cancer, Grothey says. However, these patients can develop RAS-mutant clones, which could be detected by ctDNA, Grothey explains. Moreover, patients who develop these clones will not respond to EGFR antibodies, Grothey says.

However, the RAS-mutant clones have a half-life, so by taking away the selection pressure of EGFR antibodies, the clones may disappear in 3 to 4 months, Grothey says. Testing for the presence or absence of these clones could inform whether retreatment with EGFR antibodies is warranted in a particular patient, Grothey says.

Prospectively generated data from Italy have shown that patients without RAS-mutant clones by ctDNA had a higher likelihood of responding to chemotherapy plus EGFR antibodies, Grothey says. The on-treatment monitoring approach with ctDNA could inform secondary resistance and further provide a personalized treatment approach to care for patients with CRC, concludes Grothey.