title: Attenuated familial adenomatous polyposis manifests as autosomal dominant late-onset colorectal cancer.
abstract: Colorectal cancer (CRC) risk is well defined for families of patients with classical familial adenomatous polyposis (FAP). However, the risk for those with an attenuated form of FAP is less well characterised. In this study, we estimated CRC risks for carriers of a novel germline mutation in the APC gene that causes attenuated FAP (AFAP). We performed genetic testing on 53 individuals from seven AFAP families harbouring an identical APC:c.288T>A mutation. Using a modified segregation analysis, we estimated relative and absolute CRC risks for mutation carriers. Twenty-three individuals harboured the disease causing mutation. CRC occurred in 28 individuals (mean 61.7 years, range 32-80 years). The estimated CRC relative risks for mutation carriers aged 60-69 and ≥70 years were 19 (95% CI: 1.77-204.08) and 45 (95% CI: 11.32-180.10), respectively, while the absolute CRC lifetime risk for men was 94% (95% CI: 67.5-99.9%), and for women, 84% (95% CI: 50.9-99.0%). This study shows that AFAP can manifest as autosomal dominant late-onset CRC. These findings highlight a subgroup of inherited CRCs that require new criteria for identification and surveillance.
authors.affiliation: Department of Clinical Genetics, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK.
authors.forename: Abdulla
authors.initials: A
authors.lastname: Ibrahim
authors.affiliation: Centre for Cancer Genetic Epidemiology, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Barnes
authors.affiliation: Department of Clinical Genetics, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Dunlop
authors.affiliation: Centre for Cancer Genetic Epidemiology, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Barrowdale
authors.affiliation: Centre for Cancer Genetic Epidemiology, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK.
authors.forename: Antonis C
authors.initials: AC
authors.lastname: Antoniou
authors.affiliation: Department of Clinical Genetics, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK.
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Berg
mesh_terms: D011125:Adenomatous Polyposis Coli / Q000150:complications / Q000235:genetics*; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics / Q000378:metabolism; D000328:Adult; D000368:Aged; D015179:Colorectal Neoplasms / Q000150:complications / Q000175:diagnosis / Q000235:genetics*; D005091:Exons; D005260:Female; D005820:Genetic Testing; D018095:Germ-Line Mutation; D006801:Humans; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D012307:Risk Factors; D055815:Young Adult
chemical_list: C555337:APC protein, human; D025601:Adenomatous Polyposis Coli Protein