MARKER POLYPS DO NOT CAUSE CANCER
Although serrated
polyps usually are associated with colorectal cancer, it turns out that such
polyps are themselves not dangerous, according to a Norwegian study released
this week in BMJ Gut, a journal on gastroenterology & hepatology.
As a group, person
with serrated polyps have an increased risk of intestinal cancer, on par with
persons who have high risk adenomas. Our team discovered, however, that little
happens in the polyps. This is not where the cancer develops. We believe, instead,
that large, serrated polyps may be markers of increased cancer risk," says Dr.
Øyvind Holme, primary author of the study and PhD researcher at Norwegian
hospital Sørlandet Sykehus.
Objective
Although serrated
polyps may be precursors of colorectal cancer (CRC), prospective data on the
long-term CRC risk in individuals with serrated polyps are lacking.
Design
In a population-based
randomised trial, 12 955 individuals aged 50-64 years were screened with flexible
sigmoidoscopy, while 78 220 individuals comprised the control arm. We used Cox models to
estimate HRs with 95% CIs for CRC among individuals with ≥1 large serrated
polyp (≥10 mm in diameter), compared with individuals with adenomas at screening,
and to population controls, and multivariate logistic regression to assess
polyp risk factors for CRC.
Results
A total of 103
individuals had large serrated polyps, of which 81 were included in the
analyses. Non-advanced adenomas were found in 1488 individuals, advanced
adenomas in 701. Median follow-up was 10.9 years. Compared with the control arm, the HR
for CRC was 2.5 (95% CI 0.8 to 7.8) in individuals with large serrated polyps,
2.0 (95% CI 1.3 to 2.9) in individuals with advanced adenomas and 0.6 (95% CI
0.4 to 1.1) in individuals with non-advanced adenomas. A large serrated polyp
was an independent risk factor for CRC, adjusted for histology, size and
multiplicity of concomitant adenomas (OR 3.3; 95% CI 1.3 to 8.6). Twenty-three
large serrated polyps found at screening were left in situ for a median of 11.0 years. None developed
into a malignant tumour.
Conclusions
Individuals with large
serrated polyps have an increased risk of CRC, comparable with individuals with
advanced adenomas. However, this risk may not be related to malignant growth of
the serrated polyp.
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