[giarc]

Likely that the cancers found by the sigmoid are the ones that reduce life years. Perhaps the cancers that are found and treated higher up the colon would have been found out in other ways or not serious enough? I'm not a doctor, so not sure.

[psychphysic]

Indeed there are dramatic differences between ascending and descending colon cancers.

They are also dissimilar in their chances of presenting early with symptoms making screening less useful vs those that don't present early.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6089587/