title: Systematic review of microsatellite instability and colorectal cancer prognosis.
abstract: OBJECTIVE
  A number of studies have investigated the relationship between microsatellite instability (MSI) and colorectal cancer (CRC) prognosis. Although many have reported a better survival with MSI, estimates of the hazard ratio (HR) among studies differ. To derive a more precise estimate of the prognostic significance of MSI, we have reviewed and pooled data from published studies.
  
  
  METHODS
  Studies stratifying survival in CRC patients by MSI status were eligible for analysis. The principal outcome measure was the HR. Data from eligible studies were pooled using standard techniques.
  
  
  RESULTS
  Thirty-two eligible studies reported survival in a total of 7,642 cases, including 1,277 with MSI. There was no evidence of publication bias. The combined HR estimate for overall survival associated with MSI was 0.65 (95% CI, 0.59 to 0.71; heterogeneity P = .16; I(2) = 20%). This benefit was maintained restricting analyses to clinical trial patients (HR = 0.69; 95% CI, 0.56 to 0.85) and patients with locally advanced CRC (HR = 0.67; 95% CI, 0.58 to 0.78). In patients treated with adjuvant fluorouracil (FU) CRCs with MSI had a better prognosis (HR = 0.72; 95% CI, 0.61 to 0.84). However, while data are limited, tumors with MSI derived no benefit from adjuvant FU (HR = 1.24; 95% CI, 0.72 to 2.14).
  
  
  CONCLUSIONS
  CRCs with MSI have a significantly better prognosis compared to those with intact mismatch repair. Additional studies are needed to further define the benefit of adjuvant chemotherapy in locally advanced tumors with MSI.
authors.affiliation: MRCP, Institute of Cancer Research, Brookes Lawley Building, Sutton, Surrey SM2 5NG, UK. sanjay.popat@icr.ac.uk
authors.forename: S
authors.initials: S
authors.lastname: Popat
authors.forename: R
authors.initials: R
authors.lastname: Hubner
authors.forename: R S
authors.initials: RS
authors.lastname: Houlston
mesh_terms: D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D005819:Genetic Markers; D006801:Humans; D018895:Microsatellite Repeats; D011379:Prognosis; D012189:Retrospective Studies; D016019:Survival Analysis
chemical_list: D005819:Genetic Markers