Abstract

Background/Aims
Microsatellite instability (MSI) is associated with mutations in the DNA mismatch repair system and accounts for 10-15% of all cases of sporadic colorectal cancer (CRC). However, the characteristics and role of MSI as a marker for predicting the prognosis and therapeutic effect on CRC remain unclear. Methods: Between June 2003 and December 2007, 259 patients (males, 159 [61%]; age, 63 [±11] years) who underwent surgery for CRC were retrospectively enrolled. The clinicopathologic characteristics of patients with high-frequency MSI (MSI-H) CRC were reviewed and compared to patients with low-frequency MSI or microsatellite stable CRC. The patient characteristics and MSI-related data were recorded for the following variables: gender, age, clinicopathologic findings, chemotherapy response, recurrence, and survival. Results: MSI-H CRC was diagnosed in 30 patients (12%), low-frequency MSI CRC was diagnosed in 10 patients (4%), and microsatellite stable CRC in was diagnosed in 219 patients (84%). The MSI-H group exhibited the following characteristics: large size, right colon location, positive response to chemotherapy, low recurrence, longer survival, less neural invasion, poor differentiation, diffuse lymphoid reaction, and mucin pool formation. However, in the chemotherapy group (n=180), MSI-H was not a marker of longer survival. Based on Cox-regression analysis, stage IV CRC (OR=6.66; 95% CI, 2.24-53.00), MSI-H (OR=0.17; 95% CI, 0.04-0.73), and a positive response to chemotherapy (OR=0.02; 95% CI, 0.01-0.11) were related to mortality. Conclusions: MSI-H CRC had less neural invasion and diffuse lymphoid reaction. Further studies regarding the relationship between those pathologic findings and survival are needed. (Intest Res 2009;7:14-21)

• Keywords: Colorectal Neoplasms; Microsatellite Instability; Clinico-pathological Characteristics