Prognostic significance and molecular associations of 18q loss of heterozygosity: a cohort study of microsatellite stable colorectal cancers.
OBJECTIVE
Loss of heterozygosity (LOH) at chromosome 18q frequently occurs late during colon cancer development and is inversely associated with microsatellite instability (MSI). 18q LOH has been reported to predict shorter survival in patients with colorectal cancer, whereas MSI-high status has been associated with superior prognosis. However, it is unclear whether 18q LOH in colorectal cancer has any prognostic implication independent of MSI status and other potential predictors of clinical outcome.


METHODS
Among 555 non-MSI-high colorectal cancers (stage I to IV) in two independent prospective cohort studies, we examined 18q LOH in relation to other molecular events and patient survival. Cox proportional hazard models computed hazard ratio of death, adjusted for clinical and tumoral characteristics, including KRAS, BRAF, PIK3CA, beta-catenin, p53, CpG island methylator phenotype, LINE-1 methylation, and John Cunningham (JC) virus T antigen.


RESULTS
In multivariate logistic regression, 18q LOH was independently associated with JC virus T antigen (odds ratio [OR] = 1.93; P = .0077), body mass index > or = 30 kg/m(2) (obesity; OR = 2.01; P = .014), high tumor grade (OR = 0.40; P = .018), KRAS mutation (OR = 0.66; P = .40), and LINE-1 hypomethylation (for a 30% decrease; OR = 1.92; P = .045). Five-year colorectal cancer-specific survival was 75% among patients with 18q LOH-positive tumors and 74% among those with 18q LOH-negative tumors (log-rank P = .80). Five-year overall survival was 70% among patients with 18q LOH-positive tumors and 68% among those with 18q LOH-negative tumors (log-rank P = .54). Multivariate analysis did not show prognostic significance of 18q LOH.


CONCLUSIONS
In our large prospective study of patients with non-MSI-high colorectal cancer, 18q LOH or allelic imbalance was not associated with patient survival.
Ogino
Shuji
S
Center for Molecular Oncologic Pathology, Dana-Farber Cancer Institute, Brigham and Women's Hospital, Harvard Medical School, 44 Binney St, Room JF-215C, Boston, MA 02115 USA. shuji_ogino@dfci.harvard.edu
Nosho
Katsuhiko
K
Irahara
Natsumi
N
Shima
Kaori
K
Baba
Yoshifumi
Y
Kirkner
Gregory J
GJ
Meyerhardt
Jeffrey A
JA
Fuchs
Charles S
CS
D000368:Aged; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000401:mortality*; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D005260:Female; D006801:Humans; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics; D019656:Loss of Heterozygosity; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D011518:Proto-Oncogene Proteins / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D016019:Survival Analysis; D018631:ras Proteins / Q000235:genetics
C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins
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