Are there any adverse risk factors in stage I colon cancer that would warrant ctDNA testing?

I would not check ctDNA in this setting. If there is an adverse feature of the tumor and the patient is a candidate for further treatment, I would do close surveillance imaging and CEA at the most. A recent publication of a larger cohort study of stage II to IV resected colorectal cancer suggests th...

No.

And, what would you do then? Give FOLFOX for stage 1 without real data on risk? CIRCULATE-Japan is inadequate for stage 1 data.

The risk of recurrence for T2N0 colon cancer is around 10–15% after surgery, but it can vary depending on the patient and other factors. Similar to well-described high-risk factors for recurrence in T3 N0 colon cancer (exclusive of those cancers that are MSI-H), such as poorly differentiated/undiffe...

This is a great question and we have limited data.

The best evidence would be from the CIRCULATE-Japan study which included 228 pathological stage I colon cancer patients. The positive rate in this population is extremely low in the MRD window (only 2 positive, means a positive rate of <1%) so it wi...