title: Low level microsatellite instability may be associated with reduced cancer specific survival in sporadic stage C colorectal carcinoma.
abstract: BACKGROUND
  Colorectal cancers (CRCs) may be categorised according to the degree of microsatellite instability (MSI) exhibited, as MSI-high (MSI-H), MSI-low (MSI-L), or microsatellite stable (MSS). MSI-H status confers a survival advantage to patients with sporadic CRC.
  
  
  OBJECTIVE
  To determine if low levels of MSI are related to the clinicopathological features and prognosis of sporadic stage C CRC.
  
  
  METHODS
  A total of 255 patients who underwent resection for sporadic stage C CRC were studied. No patient received chemotherapy. Minimum follow up was five years.
  
  
  METHODS
  DNA extracted from archival malignant and non-malignant tissue was amplified by polymerase chain reaction using a panel of 11 microsatellites. MSI-H was defined as instability at > or =40% of markers, MSS as no instability, and MSI-L as instability at >0% but <40% of markers. Patients with MSI-H CRC were excluded from analysis as they have previously been shown to have better survival.
  
  
  RESULTS
  Thirty three MSI-L and 176 MSS CRCs were identified. There was no difference in biological characteristics or overall survival of MSI-L compared with MSS CRC but MSI-L was associated with poorer cancer specific survival (hazard ratio 2.0 (95% confidence interval 1.1-3.6)).
  
  
  CONCLUSIONS
  Sporadic MSI-L and MSS CRCs have comparable clinicopathological features. Further studies are required to assess the impact of MSI-L on prognosis.
authors.affiliation: Conjoint Gastroenterology, Laboratory, Royal Brisbane Hospital Research Foundation Clinical Research Center, Brisbane, Australia. carolinewright@hn.ozemail.com.au
authors.forename: C M
authors.initials: CM
authors.lastname: Wright
authors.forename: O F
authors.initials: OF
authors.lastname: Dent
authors.forename: R C
authors.initials: RC
authors.lastname: Newland
authors.forename: M
authors.initials: M
authors.lastname: Barker
authors.forename: P H
authors.initials: PH
authors.lastname: Chapuis
authors.forename: E L
authors.initials: EL
authors.lastname: Bokey
authors.forename: J P
authors.initials: JP
authors.lastname: Young
authors.forename: B A
authors.initials: BA
authors.lastname: Leggett
authors.forename: J R
authors.initials: JR
authors.lastname: Jass
authors.forename: G A
authors.initials: GA
authors.lastname: Macdonald
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D042822:Genomic Instability; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D016019:Survival Analysis
chemical_list: D004273:DNA, Neoplasm