title: Combination of microsatellite instability and lymphocytic infiltrate as a prognostic indicator in colon cancer.
abstract: BACKGROUND
  Microsatellite instability (MSI) is a genetic aberration associated with less aggressive tumor biology. Some tumors with MSI also have lymphocytic infiltrate (LI), which suggests a heightened immune response against the tumor.
  
  
  OBJECTIVE
  To evaluate the combined prognostic significance of MSI and LI in a colon cancer population.
  
  
  METHODS
  Colon cancers were prospectively evaluated for MSI by assessing 11 satellite markers and were classified as MSI+ if 2 or more satellite markers displayed instability. Tumors were classified as LI+ if at least 5 lymphocytes were observed per 10 high-power fields.
  
  
  METHODS
  Community hospital system.
  
  
  METHODS
  Individuals undergoing definitive surgery for colon cancer.
  
  
  METHODS
  Overall and disease-free survival were compared according to combined MSI and LI status.
  
  
  RESULTS
  In 150 patients, tumors were classified as follows: 95 were MSI-/LI-, 9 were MSI-/LI+, 30 were MSI+/LI-, and 16 were MSI+/LI+. Median follow-up was 40.6 months. Five-year disease-free survival was 56.7% for patients with MSI-/LI- tumors and 88.9% for those with MSI+/LI+ tumors (P = .01). Patients with MSI+/LI- and MSI-/LI+ tumors had 5-year survival of 75.4% and 75.0%, respectively.
  
  
  CONCLUSIONS
  Patients with colon cancer and MSI-/LI- tumors have worse disease-free survival rate regardless of stage at diagnosis. Patients exhibiting both MSI+ and LI+ tumors have more favorable disease-free survival rates. Both MSI and LI show promise as a combined prognostic marker and with further study may prove to be particularly useful in selecting patients with stage II disease for adjunctive therapy.
authors.affiliation: Oregon Health and Science University, Department of Surgery, Portland, OR, USA.
authors.forename: Eugene Y
authors.initials: EY
authors.lastname: Chang
authors.forename: Paul B
authors.initials: PB
authors.lastname: Dorsey
authors.forename: Joseph
authors.initials: J
authors.lastname: Frankhouse
authors.forename: Randall G
authors.initials: RG
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: Nathalie
authors.initials: N
authors.lastname: Johnson
mesh_terms: D000368:Aged; D003110:Colonic Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000276:immunology* / Q000601:surgery; D006801:Humans; D008214:Lymphocytes / Q000276:immunology*; D053842:Microsatellite Instability; D011379:Prognosis; D016019:Survival Analysis