Men tend to be neoplasia prone and women neoplasia resistant

Background: Patients with a colorectal neoplasm are at risk for metachronou s neoplasia. This risk usually is stratified according to the number, size, and histology of the index lesion(s). This study was performed to search f or factors contributing not only to a very high risk of metachronous lesion s but also to a very low risk. Methods: An extensive neoplasia follow-up database was used to identify pat ients who were neoplasia prone and neoplasia resistant. Groups were defined as having consecutive colonoscopies that were either all positive or all n egative for adenoma(s). Subgroups with two, three, and four consecutive pos itive or negative examinations were formed, then analyzed for gender, numbe r of index neoplasms, and family history. Patients with familial adenomatou s polyposis or with families fulfilling the Amsterdam criteria for heredita ry nonpolyposis colorectal cancer were excluded. Results: The database showed 702 patients who had two follow-up examination s, 103 of which were neoplasia prone and 245 neoplasia resistant. After thr ee consecutive examinations (420 patients), the numbers were 51, and 87, re spectively, and after four examinations (231 patients), they were 26 and 34 . As the groups became better defined, the proportion of women in the neopl asia-resistant group and the proportion of men in the neoplasia-prone group increased. When gender and number of index lesions were combined, groups w ere most definitively characterized. Incidence of a positive family history of colorectal cancer was not different between the groups. As the number o f follow-up examinations increased, the number of large polyps found decrea sed. Conclusions: Groups of patients particularly liable to develop colorectal n eoplasia or particularly resistant to it can be identified. Female gender a nd a single-index lesion favor neoplasia resistance, whereas male gender an d multiple-index lesions favor a predisposition for neoplasia.