title: A prospective analysis of microsatellite instability as a molecular marker in colorectal cancer.
abstract: BACKGROUND
  Microsatellite instability (MSI) may be a molecular marker of colorectal tumor biology. We sought to evaluate the incidence and significance of MSI in an unselected colorectal cancer population.
  
  
  METHODS
  Colorectal cancer cases from a community health system were prospectively evaluated for MSI and patient outcomes monitored.
  
  
  RESULTS
  Of 240 eligible, 140 underwent testing; 43 (31%) had high-frequency MSI (MSI-H). Those with MSI-H tumors presented with earlier disease stage (P = .014) and lymphocytic infiltration (P < .001). Stage III MSI-H patients trended toward improved disease-free survival (P = .065). MSI-H patients were more likely to have other primary malignancies.
  
  
  CONCLUSIONS
  Prevalence of MSI-H in the general colorectal cancer population is higher than previously reported. MSI testing of colorectal cancers is useful as part of a molecular profile to stratify patients for prognosis, treatment, and further study. Patients with MSI-H tumors are more likely to have other primary malignancies, suggesting a role for heightened screening.
authors.affiliation: Legacy Health System, Surgical Associates, 1130 NW 22nd Street, Suite 500, Portland, OR 97210, USA.
authors.forename: Eugene Y
authors.initials: EY
authors.lastname: Chang
authors.forename: Paul B
authors.initials: PB
authors.lastname: Dorsey
authors.forename: Nathalie
authors.initials: N
authors.lastname: Johnson
authors.forename: Randall
authors.initials: R
authors.lastname: Lee
authors.forename: Deb
authors.initials: D
authors.lastname: Walts
authors.forename: William
authors.initials: W
authors.lastname: Johnson
authors.forename: George
authors.initials: G
authors.lastname: Anadiotis
authors.forename: Kelsey
authors.initials: K
authors.lastname: Kiser
authors.forename: Joseph
authors.initials: J
authors.lastname: Frankhouse
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D005260:Female; D042822:Genomic Instability; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D009367:Neoplasm Staging; D009922:Oregon / Q000453:epidemiology; D011379:Prognosis; D011446:Prospective Studies; D012334:RNA, Neoplasm / Q000235:genetics*; D012307:Risk Factors; D015996:Survival Rate
chemical_list: D014408:Biomarkers, Tumor; D012334:RNA, Neoplasm