I don't think I've flagged this -
On May 2, 2022, FDA released a draft guidance on use of ctDNA in early tumors. Comment is open til the end of the month.
Home page at FDA here:
Comment page at regulations.gov
https://www.regulations.gov/document/FDA-2022-D-0084-0001
Note that FDA previously produced draft and final documents on minimal residual disease in hematopoietic cancers: here.