PROGNOSTIC-SIGNIFICANCE OF MICROSATELLITE INSTABILITY IN PATIENTS WITH GASTRIC-CARCINOMA

A proportion of gastric adenocarcinomas exhibit replication errors man ifested as microsatellite instability. The clinicopathological and pro gnostic significance of this abnormality remains uncertain. This study aimed to determine the importance of microsatellite instability by an alysing a large series of gastric carcinomas from an English populatio n. Using a novel fluorescent polymerase chain reaction technique, we a mplified 11 microsatellite sequences from paired normal and carcinoma DNA from 101 patients who underwent a potentially curative resection f or gastric carcinoma. Overall, 21% of cases demonstrated microsatellit e instability in at least one locus. At least four loci were examined in each case. A replication error positive phenotype (minimum of 29% o f loci affected) was detected in 9% of cases. There was no statistical ly significant association between the presence of microsatellite inst ability or replication error positive phenotype and the patient's age, sex, tumour site, stage, node status, histological subtype or grade. Carcinomas confined to the mucosa or submucosa (T1) showed a significa ntly higher frequency of instability and replication error positive ph enotypes than T3 lesions (P = 0.03 and P = 0.05, respectively). A larg er proportion of patients who were microsatellite instability or repli cation error positive were alive at 5 years compared with those who we re negative but this did not reach statistical significance (P = 0.15 and P = 0.16, respectively). We identified a subset of gastric carcino mas from a relatively low-risk population which showed evidence of mic rosatellite instability. There were no statistically significant 5-yea r survival advantages in cases demonstrating microsatellite instabilit y or replication error positive phenotypes. The detection of microsate llite instability is of limited prognostic value in gastric carcinoma. (C) 1997 Elsevier Science Ltd.