High-risk and low-risk gastric cancer areas in Italy and its association with microsatellite instability.

PURPOSE: The different pathological characteristics and prognoses between gastric cancer patients coming from high-risk (group A) and low-risk (group B) areas of Italy were analyzed. We investigated a suspected difference in microsatellite instability (MSI) between these two groups. METHODS: MSI analyses of 452 gastric cancer patients were performed using five quasimonomorphic mononucleotide repeats NR-21, NR-24, NR-27, BAT-25, and BAT-26. MSI analysis was done by PCR usage. An allelic profile of these five mononucleotides was detected on an automated DNA sequencer ABI PRISM 3100 Genetic Analyser. Data were analyzed according to high-risk and low-risk gastric cancer areas. RESULTS: MSI was observed in 23.9 % of all gastric cancer patients studied. Patients from group A showed a higher rate of MSI (28.4 %) than from group B (13.5 %) (p < 0.001). We analyzed this association together with tumor location and Lauren classification: A nonsignificant differences were seen when analyzing cardia and non-cardia tumors (p = 0.854) but significant for Lauren histotype (p = 0.028). There was no statistical difference in survival between high-risk and low-risk areas (p = 0.437), with a nonsignificant trend for better survival in the high-risk group, especially when measured over a longer period of time. Analyzing MSI or MSS in these groups, the survival curves were almost the same. CONCLUSIONS: A higher frequency of MSI in patients coming from high-risk areas may help explain geographical differences in gastric cancer. The trend of better survival in high-risk areas may be due to a higher rate of MSI gastric cancer patients.