Identification and survival of carriers of mutations in DNA mismatch-repair genes in colon cancer.
BACKGROUND
The identification of mutations in germ-line DNA mismatch-repair genes at the time of diagnosis of colorectal cancer is important in the management of the disease.


METHODS
Without preselection and regardless of family history, we recruited 870 patients under the age of 55 years soon after they received a diagnosis of colorectal cancer. We studied these patients for germ-line mutations in the DNA mismatch-repair genes MLH1, MSH2, and MSH6 and developed a two-stage model by multivariate logistic regression for the prediction of the presence of mutations in these genes. Stage 1 of the model incorporated only clinical variables; stage 2 comprised analysis of the tumor by immunohistochemical staining and tests for microsatellite instability. The model was validated in an independent population of patients. We analyzed 2938 patient-years of follow-up to determine whether genotype influenced survival.


RESULTS
There were 38 mutations among the 870 participants (4 percent): 15 mutations in MLH1, 16 in MSH2, and 7 in MSH6. Carrier frequencies in men (6 percent) and women (3 percent) differed significantly (P<0.04). The addition of immunohistochemical analysis in stage 2 of the model had a sensitivity of 62 percent and a positive predictive value of 80 percent. There were 35 mutations in the validation series of 155 patients (23 percent): 19 mutations in MLH1, 13 in MSH2, and 3 in MSH6. The performance of the model was robust among a wide range of cutoff probabilities and was superior to that of the Bethesda and Amsterdam criteria for hereditary nonpolyposis colorectal cancer. Survival among carriers was not significantly different from that among noncarriers.


CONCLUSIONS
We devised and validated a method of identifying patients with colorectal cancer who are carriers of mutations in DNA repair genes. Survival was similar among carriers and noncarriers.
Barnetson
Rebecca A
RA
Colon Cancer Genetics Group, School of Molecular and Clinical Medicine, University of Edinburgh, Edinburgh, United Kingdom.
Tenesa
Albert
A
Farrington
Susan M
SM
Nicholl
Iain D
ID
Cetnarskyj
Roseanne
R
Porteous
Mary E
ME
Campbell
Harry
H
Dunlop
Malcolm G
MG
D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000704:Analysis of Variance; D020137:Base Pair Mismatch / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics* / Q000401:mortality; D004252:DNA Mutational Analysis; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D005838:Genotype; D018095:Germ-Line Mutation; D006579:Heterozygote; D006801:Humans; D007150:Immunohistochemistry; D016015:Logistic Models; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D011379:Prognosis; D011446:Prospective Studies; D016019:Survival Analysis
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009687:Nuclear Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein