title: Model-based prediction of defective DNA mismatch repair using clinicopathological variables in sporadic colon cancer patients.
abstract: BACKGROUND
  : Colon cancers with defective DNA mismatch repair (MMR) have a favorable prognosis and may lack benefit from 5-fluorouracil-based adjuvant chemotherapy. The authors developed models to predict MMR deficiency in sporadic colon cancer patients using routine clinical and pathological data.
  
  
  METHODS
  : TNM stage II and III colon carcinomas (n = 982) from 6 5-fluorouracil-based adjuvant therapy trials were analyzed for microsatellite instability and/or MMR protein expression. Tumor-infiltrating lymphocytes (TILs) were quantified (n = 326). Logistic regression and a recursive partitioning and amalgamation analysis were used to identify predictive factors for MMR status.
  
  
  RESULTS
  : Defective MMR was detected in 147 (15%) cancers. Tumor site and histologic grade were the most important predictors of MMR status. Distal tumors had a low likelihood of defective MMR (3%; 13 of 468); proximal tumors had a greater likelihood (26%; 130 of 506). By using tumor site, grade, and sex, the logistic regression model showed excellent discrimination (c statistic = 0.81). Proximal site, female sex, and poor differentiation showed a positive predictive value (PPV) of 51% for defective MMR. In a patient subset (n = 326), a model including proximal site, TILs (>2/high-power field), and female sex showed even better discrimination (c statistic = 0.86), with a PPV of 81%.
  
  
  CONCLUSIONS
  : Defective MMR is rare in distal, sporadic colon cancers, which should generally not undergo MMR testing. Proximal site, poor differentiation, and female sex detect 51% of tumors with defective MMR; substituting TILs for grade increases the PPV to 81%. These data can increase the efficiency of MMR testing to assist in clinical decisions. Cancer 2010. (c) 2010 American Cancer Society.
authors.affiliation: Division of Oncology, Mayo Clinic, Rochester, Minnesota, USA. sinicrope.frank@mayo.edu
authors.forename: Frank
authors.initials: F
authors.lastname: Sinicrope
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Foster
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Sargent
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Thibodeau
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Smyrk
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Connell
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D053843:DNA Mismatch Repair; D005260:Female; D005544:Forecasting; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological