Microsatellite instability in gastric cancer is associated with better prognosis in only stage II cancers.
BACKGROUND
The assessment of microsatellite instability (MSI) is not included yet in the routine evaluation of patients with gastric cancer, as controversial data exist regarding its prognostic value.


METHODS
We determined the clinical significance of MSI in 510 sporadic gastric cancers, using the mononucleotide markers BAT25 and BAT26. The results were compared with the immunohistochemical expression of the mismatch repair proteins Mlh1 and Msh2.


RESULTS
MSI was present in 83 (16%) cancers and correlated with better survival (P < .001). Multivariate analysis showed that the MSI phenotype was an independent factor (P = .005) and added prognostic information to TNM stage, location, and age. The relative risk of death for MSI cancer patients was 0.6 (95% confidence interval [CI], 0.4-0.8). Moreover, when grouped according to stage, only stage II cancers showed a significant effect of MSI status on survival (P = .011; hazard ratio = 0.3; 95% CI, 0.1-0.8). MSI also correlated with older age (P = .002), female gender (P < .001), intestinal histotype (P = .011), lower T stage (P = .018), and less lymph node involvement (P < .001). Finally, comparison of the results of immunohistochemical expression of the mismatch repair proteins Mlh1 and Msh2 with microsatellite analysis showed concordant results in 95% of neoplasms, with a sensitivity of 82% and specificity of 98%.


CONCLUSIONS
Microsatellite analysis of gastric cancer has clinical utility in determination of prognosis, but should be determined in only stage II neoplasms in a routine clinical setting. Immunohistochemistry may be considered sufficient, although microsatellite analysis is preferable.
Department of Pathology, Section of Anatomical Pathology, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy.
Stefania
S
Beghelli
Giovanni
G
de Manzoni
Stefano
S
Barbi
Anna
A
Tomezzoli
Franco
F
Roviello
Carmela
C
Di Gregorio
Carla
C
Vindigni
Laura
L
Bortesi
Alice
A
Parisi
Luca
L
Saragoni
Aldo
A
Scarpa
Patrick S
PS
Moore
D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D042822:Genomic Instability; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D015999:Multivariate Analysis; D009367:Neoplasm Staging; D011379:Prognosis; D012189:Retrospective Studies; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology*; D016019:Survival Analysis