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An update on APC p.I1307K homozygosity: Observations from 74 individuals from a large multigene panel testing cohort

Session:
#9017
Date:
Thursday, Oct 16, 2025 2:30pm – 4:30pm
Conference:
ASHG 2025
Authors:
Aimee Lucas, Carrie Horton, Leah Zaretsky, Linda Polfus, Magan Trottier, Marcy E. Richardson, Taylor D. Coleman
Collaborators:

Presenting Author: Marcy E. Richardson, PhD

Take home points: 

  • APC I1307K homozygotes trend towards increased odds of CRC (OR 2.479 [0.914-6.723], p 0.074) but no difference in age at CRC diagnosis relative to other control cohorts.
  • Small effect sizes continue to limit the ability to detect significantly distinct odds of CRC between APC I1307K heterozygotes and homozygotes necessitating as many as 567 homozygotes to detect an odds of CRC of 1.78 (similar to literature heterozygotes 1
  • In this cohort, MSH6-positives have a statistically significant odds of CRC (OR 4.98, p<.001). Power calculations support ability to detect an OR of 4 given current sample sizes. Therefore, APC I1307K homozygotes do not have risks similar to MSH6-related Lynch Syndrome
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