Purpose: Several studies have shown that the clinical phenotype of patients with familial adenomatous polyposis is influenced by the position of the associated germline mutation in the APC gene. The aim of this work was to assess whether the site of the APC mutation may also predict the survival of familial adenomatous polyposis patients with a confirmed diagnosis of colorectal cancer.
Methods: A total of 387 familial adenomatous polyposis patients with colorectal cancer were examined. Of these, 287 (74 percent) belonged to families with an identified mutation, whereas 100 (26 percent) were from families in which no detectable APC mutation had been found by standard screening methods. The subjects were subdivided into four groups, according to the presence and localization of the identified mutation: with mutation before (a), at (b), or beyond codon 1309 (c), and without identified mutation (d).
Results: The cumulative five-year survival estimate of all cases included in the study was 0.56 (95 percent confidence interval, 0.51-0.61). No difference was observed in survival probability among patients from families with mutations before (0.56; 95 percent confidence interval, 0.49-0.63), at (0.58; 95 percent confidence interval, 0.43-0.72), or beyond (0.52; 95 percent confidence interval, 0.31-0.73) codon 1309 or those from families that were mutation negative (0.58; 95 percent confidence interval, 0.48-0.68) (log-rank test, P = 0.9). Survival analysis did not reveal any significant advantage for patients carrying a mutation in a specific region of the APC gene, after adjustment for age, gender, site, and stage.
Conclusion: These data do not support the hypothesis that APC mutation may influence the outcome of familial adenomatous polyposis cases affected by colorectal cancer.