Use of microsatellite analysis in young patients with colorectal cancer to identify those with hereditary nonpolyposis colorectal cancer

BACKGROUND AND OBJECTIVES: The frequency of microsatellite instability (MSI) in young patients with colorectal cancer was evaluated, including reexamination of the medical and family history of each patient, and interviews with the patients to determine any possible new occurrence of hereditary nonpolyposis colorectal cancer (HNPCC) in the patients themselves or their family members. METHODS: Fifty-three young patients (younger than 40 years of age) with colorectal cancer were selected and investigated. DNA was extracted from paraffin sections and microsatellite analysis was performed. RESULTS: The frequency of MSI among the young patients with colorectal cancer was 50.9%, which was significantly higher than the rate of 12-21% noted in older patients with colorectal cancer (P < 0.001). For the 24 young patients with colorectal cancer who did not have MSI, only one case of HNPCC kindred and two cases with a family history of cancer were identified. In contrast, among the 20 young patients with colorectal cancer who had MSI, five cases of HNPCC kindred, two cases with metachronous patients with colorectal cancer, and three cases with a family history of cancer were identified. CONCLUSION: Our results suggest that a defect in the DNA mismatch repair system may play some role in carcinogenesis in young patients with colorectal cancer. Microsatellite analysis and subsequent interviews regarding medical and family history are useful tools for efficiently identifying possible cases of HNPCC among young patients with colorectal cancer.