Purpose of investigation: Microsatellite instability (MSI) is a hallmark of defective mismatch repair and is present in approximately 20% of ovarian cancers. It is not known if the presence of MSI predicts survival in women with epithelial ovarian cancer.
Materials and methods: Cases of epithelial ovarian cancer were ascertained from a population-based study in Ontario and tumour samples were tested for MSI, using five MSI markers. Patients were divided into MSI-high and MSI-low/normal, according to National Cancer Institute criteria. The authors compared the prevalence of specific prognostic factors in the two subgroups, including age, grade, stage, and histology. They estimated the hazard ratio for death from ovarian cancer associated with MSI-high and with other prognostic factors using a multi-variate analysis.
Results: A total of 418 ovarian cancer patients were included. One hundred and twenty-seven (19.7%) cancers were MSI- high. Subgroup analyses did not reveal any statistically significant differences for pathologic features associated with MSI status. No survival difference was seen according to MSI status.
Conclusions: The presence of MSI in ovarian cancer is not associated with survival.