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This is some interesting data.
The Winawer study was the National Polyp Study that took people with adenomas and then
followed them with surveillance colonoscopy at one to three years up to six years. What
they found after the observation was only five cases of cancer, and this was far less than
historical controls. So they inferred from this that colonoscopy will wipe out colon
cancer. There have been a bunch of polyp prevention trials, including one we participated
in, the Schatzkin study, which took people with adenomas. It was a dietary intervention
study using wheat bran to see if you could prevent the recurrence of adenomas. They looked
at the cancer rate in these 2000 people that were being followed and in fact the incidence
rate is not negligible by any means, and was in fact somewhat similar to C rate (?). What
does this mean? It means first of all that colonoscopy is not perfect: people think they
got to the end of the colon when they really didn’t, you can miss lesions with
colonoscopy, or there are now a lot of data about flat adenomas – adenomas that are not
so easily detectable – that maybe progress further on. |