Classification of Microsatellite Alterations Detected in Endoscopic Biopsy Specimens of Gastric Cancers

PURPOSE: Individual gastric cancers demonstrate complicated genetic alterations. The PCR-based analysis of polymorphic microsatellite sequences on cancer-related chromosomes has been used to detect chromosomal loss and microsatellite instability. For the purpose of preoperative usage, we analyzed the correspondance rate of the microsatellite genotype between endoscopic biopsy and surgical specimens. MATERIALS AND METHODS: Seventy-three pairs of biopsy and surgical specimens were examined for loss of heterozygosity and microsatellite instability by using 40 microsatellite markers on eight chromosomes. Microsatellite alterations in tumor DNAs were classified into a high-risk group (baseline- level loss of heterozygosity: 1 chromosomal loss in diffuse type and high-level loss of heterozygosity: 4 or more chromosomal losses) and a low-risk group (microsatellite instability and low-level loss of heterozygosity: 2 or 3 chromosomal losses in diffuse type or 1~3 chromosomal losses in intestinal type) based on the extent of chromosomal loss and microsatellite instability. RESULTS: The chromosomal losses of the biopsy and the surgical specimens were found to be different in 21 of the 73 cases, 19 cases of which were categorized into a genotype group of similar extent. In 100 surgical specimens, the high-risk genotype group showed a high incidence of nodal involvement (19 of 23 cases: 5 cm) irrespective of tumor size while the incidence of nodal involvement for the low-risk genotype group depended on tumor size (5 of 26 cases: 5 cm). Extraserosal invasion was more frequent in large-sized tumor in both the high-risk genotype group (5 cm: 23 of 24 cases) and the low-risk genotype group (5 cm: 16 of 27 cases). The preoperative prediction of tumor invasion and nodal involvement based on tumor size and genotype corresponded closely to the pathologic tumor stage (ROC area>0.7). CONCLUSION: An endoscopic biopsy specimen of gastric cancer can be used to make a preoperative genetic diagnosis that accurately reflect the genotype of the corresponding surgical specimen.

Comparative Study by Primary Tumor (T) and Nodal Involvement (N) in Stage II Gastric Cancer

PURPOSE: This study was done to evaluate the differences in clinical parameters and survival rates between the primary tumor (T) and nodal involvement (N) in stage II cancers. METHODS: This report is a retrospective clinical analysis of 100 patients of stage II gastric cancer who were treated surgically at the Department of Surgery, Chonbuk National University Hospital from Jan. 1990 to Dec. 1999. Among the 100 patients, the pT3N0 group included 48 patients, and the pT2N1 group 52 patients. In this study, we used the UICC TNM staging system (the fourth edition). RESULTS: There were no significant differences except for age and tumor sizes between the pT3N0 and the pT2N1 groups with regard to the mode of presentation, sex, location of tumor, type of resection, lymph node dissection, Borrmann and Lauren classification, cell cytology, recurrence, number of resected lymph nodes, and the 5-year survival rate. Based on the number of lymph nodal metastases, no significant difference was observed in the 5-year survival rate, but based on the ratio of lymph nodal metastases, the 5-year survival rate for those with up to 20% frequency of metastases was 85.2% and the 5-year survival rate for those with greater than 20% was 40.0%, which is significant difference in the 5-year survival rate. CONCLUSION: In stage II gastric cancer, there was no difference between the pT3N0 and the pT2N1 group, except that in the pT2N1 group, a subdivision of the pN stage according to the ratio of lymph nodal metastases could be successfully applied to the clinical evaluation of stage II gastric cancer.