Partly by pathology - locations and markers, partly by doubling times, partly soft indicators. Nothing is 100%, but with all the normal information and a little extra blood work, someone really expert could get a pretty good idea even in the opening days and be close enough to improve the prognosis.
I think many KRAS/BRAF mutant patients lose years during the first weeks or month, post diagnosis, because of less than optimal approaches to data collection, interpretation, and treatment. How decisions change your life
, from Mr Destiny
I might point out, that for many BRAF/KRAS mutant patients, especially advanced stage BRAF mutant CRC, the extra blood tests done initially for minor costs on the first day, might be intelligently used to get genetic testing started on the 2nd
day after diagnosis. There's a lot of wasted potential there.