Clinical value of screening hereditary nonpolyposis colorectal cancer in China with protocol recommended by NCCN guidelines

Objective To investigate the effect of the protocol recommended by NCCN-2007 on the diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC) in China. Methods NCCN protocol consists of identifying HNPCC characteristics according to the revised Bethesda Guidelines, genetic counseling with immunohistochemistry and finally genetic testing. Four hundred and nintecn patients diagnosed as colorectal cancer from January 2002 to February 2006 were selected. The hMLH1 and hMSH2 immunostaining were implemented for 90 patients who fulfilled the revised Bethesda Guidelines, in whom 8 patients fulfilling the Amsterdam Ⅱ Criteria were classified as group A and the other 82 patients as group B. The frozen tissues were collected from patients who showed loss of hMLH1 or hMSH2 protein expression, then RNA was extracted, and RT-PCR and cDNA sequencing were adopted to detect the garmline mutations of hMLH1 and hMSH2. Results Tumor tissues from 18 patients showed loss of hMLH1 or hMSH2 protein expression (5 patients in group A and 13 in group B). Finally, 21 patients(8 in group A and 13 in group B showed loss expression of MMR protein) were diagnosed as HNPCC, including 2 cases of hMLH1 and 1 case of hMSH2 mutations. These 3 cases with cDNA mutations did not fulfill the Amsterdam Ⅱ Criteria, and were finally diagnosed as HNPCC. Conclusion The protocol recommended by NCCN-2007 offers a useful approach to identify HNPCC patients, and reduces the possibility of missed diagnosis of HNPCC. Key words: Colorectal neoplasms, hereditary nonpolyposis;  Revised Betheeda Guidelines; Diagnosis