Prognostic factors in sporadic colon cancer with high-level microsatellite instability

The microsatellite instability-high (MSI-H) phenotype of colon cancer has a good prognosis and limited response to chemotherapy. We aimed to investigate prognostic factors and oncologic outcomes in patients with MSI-H sporadic colon cancer.

A total of 329 patients with MSI-H sporadic colon cancer who underwent radical surgery from January 2004 to December 2012 at a single institution were included. We analyzed prognostic factors and oncologic outcomes according to chemotherapy in these patients compared with patients with MSI-low/microsatellite stable colon cancer.

Among the 329 patients, 174 were male and 155 were female. The median age was 59 years. The population consisted of 220 patients with stage II, 97 with stage III, and 12 with stage IV disease. Old age and advanced stage were independent poor prognostic factors of overall survival (OS; P = .014 and P = .040, respectively) and advanced stage and presence of perineural invasion were independent poor prognostic factors of disease-free survival (DFS; P = .004 and P = .001, respectively). In addition, a greater number of poor prognostic factors were associated with worse survival (P < .001). Patients with stage II disease showed no differences in OS and DFS according to receiving or not receiving chemotherapy (P = .140 and P = .694, respectively).

Old age, advanced stage, and presence of perineural invasion were independent and poor prognostic factors in patients with MSI-H sporadic colon cancer. Survival rates of MSI-H colon cancer patients with stage II disease were not improved by adjuvant chemotherapy.