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EARLY COLECTOMY, FEMALE GENDER, AND GENETIC PREDISPOSITION ARE ASSOCIATED WITH THE DEVELOPMENT OF DESMOID TUMOURS IN FAMILIAL ADENOMATOUS POLYPOSIS

C Durno, T Berk, N Monga, Z Cohen, S Gallinger
Familial Gastrointestinal Cancer Registry, Mount Sinai Hospital, Hospital for Sick Children, University of Toronto, Toronto, Ontario

BACKGROUND: Desmoid tumours are rare, non-metastasising fibromatoses that occur in 10-20% of subjects with familial adenomatous polyposis (FAP). Intra-abdominal desmoid tumours are a major source of morbidity, and are one of the common causes of death in these patients. FAP-associated desmoid tumours are linked to trauma, particularly abdominal surgery, family history of desmoids, hormonal factors, and the location of the APC germline mutation. Prophylactic colectomy at an early age may increase the risk of developing desmoids.
AIM: The aims of this study were to determine: (1) if colectomy earlier in life is a risk factor for the development of symptomatic desmoid tumours, and (2) if gender, APC genotype, and family history of desmoids are risk factors in the development of desmoids in FAP.
METHODS: The association between desmoid development and age at colectomy, family history of desmoids, gender, and APC mutation was reviewed in FAP patients entered in the FAP Registry (1980-2005).
RESULTS: Patients with FAP (n=930) from 365 kindreds were identified. Desmoid prevalence was 14% (n=121).The mean age at diagnosis of desmoid was 32.1 years (SD 11.9 years). Females were more likely to develop desmoids than males (17 versus 11%, p=0.03). Multivariate analysis showed that females who underwent an early colectomy (<=18 years) are 2.5 times more likely to develop symptomatic desmoids, compared to males who undergo a late colectomy (p=0.05).Females who undergo an early colectomy are more than two times more likely to develop a desmoid, compared to women undergoing a colectomy >18 years (p=0.01). Early colectomy did not increase risk of developing a desmoid in males (p=0.42). The APC mutation was known in 457 patients: the prevalence of desmoids in the 5' and 3' groups was 13% and 38%, respectively (p=0.0005).
CONCLUSIONS: Females with FAP are more likely to develop desmoids than males. Females who undergo an early colectomy are at a significantly greater risk of developing a desmoid compared to females who undergo a colectomy in adulthood. Patients with APC mutations proximal to codon 1399 are more likely to develop desmoids. These results suggest that delayed colectomy might be considered in young females with FAP in order to decrease the chances of developing desmoid tumours.

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