Mine is hereditary (diagnosed at 42) so the protocol for my kids would be genetic testing around 18-25, then they would also start colonoscopies at 25 or so.
The gene that likely was the primary driver for mine is one of the Lynch genes that is not associated with obvious suite of other cancers - there really was no family history, which certainly caught me off guard. Dad is in mid 70's, carries the same gene (had testing done after my diagnosis), and has had a few polyps but nothing else... If I would have known I carried this, I would have started colonoscopies much earlier and likely it would have been caught.
42 yr old male
Diagnosed December 2016, age 41
Stage 1/IIA rectal cancer - T2/3N0M0 via MRI (MRI indicates stage 1; onc/surgeon = stage 2a)
Lynch syndrome, MSH6 mutation, MSI
2 to 3/2017 Xeloda + Radiation
5/10/17 - Robotic LAR with temp. loop illeostomy, 0/20 lymph nodes
6 to 7/2017 - Six cycles Folfox @ full strength
9/20/17 - Ileostomy takedown
10/17 - Clear CT
1/18 - 5mm polyp removed during colonoscopy