title: Microsatellite instability of the colorectal carcinoma can be predicted in the conventional pathologic examination. A prospective multicentric study and the statistical analysis of 615 cases consolidate our previously proposed logistic regression model.
abstract: High microsatellite instability (MSI-H) allows the identification of a subset of colorectal carcinomas associated with good prognosis and a higher incidence of Lynch syndrome. The aim of this work was to assess the interobserver variability and optimize our MSI-H prediction model previously published based on phenotypic features.The validation series collected from five different hospitals included 265 primary colorectal carcinomas from the same number of patients. The eight clinicopathological parameters that integrate our original model were evaluated in the corresponding centers. Homogeneity assessment revealed significant differences between hospitals in the estimation of the growth pattern, presence of Crohn-like reaction, percentage of cribriform structures, and Ki-67 positivity. Despite this observation, our model was globally able to predict MSI-H with a negative predictive value of 97.0%. The optimization studies were carried out with 615 cases and resulted in a new prediction model RERtest8, which includes the presence of tumor infiltrating lymphocytes at the expense of the percentage of cribriform structures. This refined model achieves a negative predictive value of 97.9% that is maintained even when the immunohistochemical parameters are left out, RERtest6. The high negative predictive value achieved by our models allows the reduction of the cases to be tested for MSI to less than 10%. Furthermore, the easy evaluation of the parameters included in the model renders it a useful tool for the routine practice and can reinforce other published models and the current clinical protocols to detect the subset of colorectal cancer patients bearing hereditary nonpolyposis colorectal cancers risk and/or MSI-H phenotype.
authors.affiliation: BIOPAT. Biopatologia Molecular, SL, Grup Assistència, Avda. Diagonal 660, Barcelona, Spain. rroman@biopat.es
authors.forename: Ruth
authors.initials: R
authors.lastname: Román
authors.forename: Montse
authors.initials: M
authors.lastname: Verdú
authors.forename: Miquel
authors.initials: M
authors.lastname: Calvo
authors.forename: August
authors.initials: A
authors.lastname: Vidal
authors.forename: Xavier
authors.initials: X
authors.lastname: Sanjuan
authors.forename: Mireya
authors.initials: M
authors.lastname: Jimeno
authors.forename: Antonio
authors.initials: A
authors.lastname: Salas
authors.forename: Josefina
authors.initials: J
authors.lastname: Autonell
authors.forename: Isabel
authors.initials: I
authors.lastname: Trias
authors.forename: Marta
authors.initials: M
authors.lastname: González
authors.forename: Beatriz
authors.initials: B
authors.lastname: García
authors.forename: Natalia
authors.initials: N
authors.lastname: Rodón
authors.forename: Xavier
authors.initials: X
authors.lastname: Puig
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000235:genetics*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
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