Accuracy of revised Bethesda guidelines, microsatellite instability, and immunohistochemistry for the identification of patients with hereditary nonpolyposis colorectal cancer.
BACKGROUND
The selection of individuals for hereditary nonpolyposis colorectal cancer (HNPCC) genetic testing is challenging. Recently, the National Cancer Institute outlined a new set of recommendations, the revised Bethesda guidelines, for the identification of individuals with HNPCC who should be tested for microsatellite instability.


OBJECTIVE
To establish the most effective and efficient strategy for the detection of MSH2/MLH1 gene carriers.


METHODS
A prospective, multicenter, nationwide study (the EPICOLON study) in 20 hospitals in the general community in Spain of 1222 patients with newly diagnosed colorectal cancer between November 1, 2000, and October 31, 2001.


METHODS
Microsatellite instability testing and MSH2/MLH1 immunostaining in all patients regardless of age, personal or family history, and tumor characteristics. Patients whose tumors exhibited microsatellite instability and/or lack of protein expression underwent MSH2/MLH1 germline testing.


METHODS
Effectiveness and efficiency of both microsatellite instability testing and immunostaining, either directly or previous selection of patients according to the revised Bethesda guidelines, were evaluated with respect to the presence of MSH2/MLH1 germline mutations.


RESULTS
Two hundred eighty-seven patients (23.5%) fulfilled the revised Bethesda guidelines. Ninety-one patients (7.4%) had a mismatch repair deficiency, with tumors exhibiting either microsatellite instability (n = 83) or loss of protein expression (n = 81). Germline testing identified 11 mutations (0.9%) in either MSH2 (7 cases) or MLH1 (4 cases) genes. Strategies based on either microsatellite instability testing or immunostaining previous selection of patients according to the revised Bethesda guidelines were the most effective (sensitivity, 81.8% and 81.8%; specificity, 98.0% and 98.2%; positive predictive value, 27.3% and 29.0%, respectively) to identify MSH2/MLH1 gene carriers. Logistic regression analysis confirmed the revised Bethesda guidelines as the most discriminating set of clinical parameters (odds ratio, 33.3; 95% confidence interval, 4.3-250; P = .001).


CONCLUSIONS
The revised Bethesda guidelines constitute a useful approach to identify patients at risk for HNPCC. In patients fulfilling these criteria, both microsatellite instability testing and immunostaining are equivalent and highly effective strategies to further select those patients who should be tested for MSH2/MLH1 germline mutations.
Piñol
Virgínia
V
Department of Gastroenterology, Institut de Malalties Digestives, Hospital Clínic, University of Barcelona, Barcelona, Spain.
Castells
Antoni
A
Andreu
Montserrat
M
Castellví-Bel
Sergi
S
Alenda
Cristina
C
Llor
Xavier
X
Xicola
Rosa M
RM
Rodríguez-Moranta
Francisco
F
Payá
Artemio
A
Jover
Rodrigo
R
Bessa
Xavier
X
D048868:Adaptor Proteins, Signal Transducing; D000368:Aged; D002352:Carrier Proteins; D043171:Chromosomal Instability; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000175:diagnosis* / Q000235:genetics* / Q000378:metabolism; D003362:Cost-Benefit Analysis; D004252:DNA Mutational Analysis / Q000191:economics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006580:Genetic Carrier Screening; D005820:Genetic Testing / Q000191:economics / Q000592:standards*; D018095:Germ-Line Mutation; D017408:Guidelines as Topic; D006579:Heterozygote; D006801:Humans; D007150:Immunohistochemistry / Q000191:economics; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D012680:Sensitivity and Specificity; D013030:Spain
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein