Background: The data describing the extracolonic cancers associated with hereditary nonpolyposis colorectal cancer (HNPCC) are variable.
Methods: We ascertained all Amsterdam I criteria-positive pedigrees (N = 18) in the Utah Population Database (UPDB). We identified the extracolonic cancers in the colorectal cancer cases (N = 65) in these pedigrees, and in their first- (N = 509) and second-degree (N = 1,611) relatives. Standardized morbidity ratios were estimated by comparing the observed rates of extracolonic cancer in defined sets of relatives of probands with population expected rates estimated internally from the UPDB.
Results: The extracolonic cancers observed in significant excess in the 65 Amsterdam I criteria-positive colorectal cancer (CRC) cases in the UPDB were uterine (N = 3, p = 0.003), lip (N = 2, p = 0.007), stomach (N = 2, p = 0.009), female genitalia (N = 1, p = 0.004) and larynx (N = 1, p = 0.05). Extracolonic cancers observed in significant excess in the 509 first-degree relatives of the 65 colorectal cancer (CRC) cases in these Amsterdam I criteria pedigrees included: thyroid (N = 5, p = 0.0002) and prostate (N = 19, p = 0.002). Thyroid cancer (N = 6, p = 0.003) was found in significant excess in the second-degree relatives of the Amsterdam I criteria-positive CRC cases.
Conclusions: In this population-based examination of the extracolonic cancers at excess in classic HNPCC pedigrees (selected by Amsterdam I criteria) we not only observed many of the same cancers previously reported to be associated with HNPCC in both CRC probands and their relatives, but also identified several previously unreported associations. Although our sample size is small, this study is population based, lacks ascertainment and recall bias, and benefits from uniform, consistent diagnoses of all cancers in a statewide registry.