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Factors associated with precancerous colon polyps (adenomas) in Lynch syndrome patients

Cancer Genetics and Therapeutics
  • Primary Categories:
    • Cancer
  • Secondary Categories:
    • Cancer
Introduction:
Patients with Lynch syndrome have an elevated risk for colon cancer and are recommended to have a colonoscopy every one to three years. A colonoscopy is performed to identify precancerous polyps (adenomas), which are removed at the time of the procedure to prevent colon cancer. Many Lynch syndrome patients are unable to undergo frequent colonoscopies due to limited access, financial constraints, and other roadblocks. Targeting colonoscopy to Lynch syndrome patients at high risk for adenoma development would allow for more efficient use of resources and improved cancer prevention. There has been little research on risk factors for adenoma development in Lynch syndrome patients. Adenoma detection is usually measured as the percentage of colonoscopies with an adenoma detected (adenoma detection rate (ADR)). To gain further insights, we studied ADRs in a large set of Lynch syndrome patient colonoscopies.  

Methods:
We reviewed the records of Lynch syndrome patients enrolled in a single-center colonoscopy program from 2009 to 2024. All patients had pathogenic or likely pathogenic variants in one of the Lynch syndrome DNA mismatch repair genes: MLH1, MSH2/EPCAM, MSH6, or PMS2

Results:
One hundred and fifty Lynch syndrome patients had 509 colonoscopies. Most patients were female (65%), and the mean age at the first colonoscopy was 54 years old. An adenoma was found at about one out of three colonoscopies (36.5%, 186/509). ADR by colonoscopy number was first (43%), second (37%), third (34%), fourth (30%) and fifth (19%) (p=0.006).  One patient was diagnosed with colon cancer at their first colonoscopy. Otherwise, no other patient was diagnosed with colon cancer. Colonoscopies with an adenoma had a mean patient age of 57 years old versus 51 years old for those colonoscopies without an adenoma (p<0.001). ADRs were similar when colonoscopy ADRs were studied by mismatch repair gene with a pathogenic variant (MLH1 colonoscopies= 39%, MSH2/EPCAM colonoscopies= 36%, MSH6 colonoscopies= 36%, PMS2 colonoscopies= 34%). There was no difference in ADRs when reviewed by sex, body mass index categories, having an adenoma found at a previous colonoscopy, or history of surgery to remove a section of the colon for colon cancer (colectomy) (all p>0.05). 

Conclusion:
Adenomas were more common in Lynch syndrome patients with increasing age and less common with each successive colonoscopy. Interestingly, many factors thought to increase the risk for colon cancer in Lynch syndrome were not confirmed as risk factors for adenomas, including a history of colon cancer surgery and a specific mismatch repair gene with a pathogenic variant (MLH1, MSH2 higher risk of colon cancer). It could be that there are separate risk factors for adenoma and cancer development. The risk factors for adenomas that we have identified should be investigated to be included in an algorithm to risk stratify patients and target colonoscopies accordingly.  

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