Abstracts from the 11th Annual Meeting of the Collaborative Group of the Americas on Inherited Colorectal Cancer (CGA-ICC), October 21–22, 2007, La Jolla, California, USA

Background: Routine genetic testing is costly and not widely available in Asia. A thorough family history remains the most important and cost-effective means of diagnosing hereditary non-polyposis colorectal cancer (HNPCC). However, the usefulness of the Amsterdam criteria for diagnosis of HNPCC in Asians has not been thoroughly evaluated. This study aims to characterize the phenotype of Amsterdam-defined Asian HNPCC patients registered with the Singapore Polyposis Registry since 1989. Methods: A review was conducted of HNPCC patients registered with the Singapore Polyposis Registry over a 16-year period. All patients fulfilled the Amsterdam I and II criteria. Data on demographics, site of colorectal cancers, synchronous cancers, associated extra-colonic cancers in pedigrees, histology, type of colonic resections, Dukes’ and TNM staging were obtained from a prospective computerized database. Results: A total of 52 patients with colorectal cancer from Amsterdam-defined HNPCC families were reviewed. The male to female ratio was 1.6:1 with median age of 44.5 years (range 27-73) at diagnosis of first cancer. The ethnic distribution was 47 Chinese (91%) and 5 Malays (9%), and the median follow up was 44.9 months (range 2-183 months). More than two thirds (69%) of the tumours were left-sided, with the majority located in the sigmoid colon. More than half (60%) of the tumours presented at a late stage (Dukes’ C&D), with 83% being moderately or poorly differentiated adenocarcinomas. Left-sided tumours tend to have more advanced Duke’s stage disease (p=0.096) and a higher rate of metastasis (p=0.08) compared to right-sided lesions. There was, however, no significant difference in disease-free or overall survival between left and right-sided tumours. Conclusions: In contrast to data from studies on Caucasian populations, Amsterdam-defined Asian HNPCC families appeared to have more left-sided tumours. These differences may be due to inadequacies of the Amsterdam criteria when applied to an Asian population or a true ethnic variation in HNPCC phenotypic expression. Further studies are needed to clarify the genotypic-phenotypic correlations and the usefulness of the Amsterdam criteria in diagnosis of HNPCC in Asian populations.