title: Colorectal liver metastases are more often super wild type. Toward treatment based on metastatic site genotyping?
abstract: Recent data showed that metastatic colorectal (mCRC) tumors exhibiting extended RAS-BRAF mutations were resistant to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies, making these drugs suitable for the so-called "super" wild-type (WT) patients only. This study aimed to compare the extended RAS-BRAF mutation frequency and characteristics according to location of tumor sampling. All consecutive mCRC specimens (N = 1659) referred to our institution from January 2008 till June 2014 were included in the analysis. Tumor genotyping (first for KRAS exon 2, then for BRAF exon 15, and later for KRAS exons 2, 3, and 4 and NRAS exons 2, 3, and 4) was performed with high-resolution melting analysis or allelic discrimination. The factors predicting for the presence of mutation were explored using multivariate binary logistic regression. Overall, the prevalence of KRAS exon 2 was 36.8%, and it was lower in liver metastases (N = 138/490; 28.2%) in comparison with primary tumors (N = 442/1086; 40.7%), lung metastases (16/32; 50%), or other metastatic sites (15/51; 29.4%; P < 0.0001). Similarly, in the 1428 samples analyzed, BRAF mutations were less often found in liver metastases (N = 9/396; 2.3%) as compared to primary tumors (N = 79/959; 8.2%), lung metastases (N = 2/29; 6.9%), or other metastatic locations (N = 2/44; 4.5%; P < 0.0002). Overall occurrence of extended RAS mutation was 51.7%. Of the 503 samples tested, the prevalence of extended RAS-BRAF mutations was twice as low in liver metastases (N = 53/151; 34.2 %) as compared to primary tumors (N = 191/322; 59.3%, P < 0.0001). Univariate analysis identified age ≤65 years, male gender, and liver localization as predictors of super WT status. At multivariate analysis, only liver metastases were retained (RR 2.85 [95% CI 1.91-4.30]). Colorectal liver metastases are twice as likely to exhibit a super WT genotype as compared to other tumor locations independently from other factors. This molecular feature has the potential to influence therapeutic strategy in mCRC patients.
authors.affiliation: APHP, Biochemistry and Oncogenetic Department, Paul Brousse Hospital, Groupe Hospitalier de Hôpitaux Universitaires Paris-Sud, Villejuif, France.
authors.forename: M A
authors.initials: MA
authors.lastname: Allard
authors.forename: R
authors.initials: R
authors.lastname: Saffroy
authors.forename: P Bouvet
authors.initials: PB
authors.lastname: de la Maisonneuve
authors.forename: L
authors.initials: L
authors.lastname: Ricca
authors.forename: N
authors.initials: N
authors.lastname: Bosselut
authors.forename: J
authors.initials: J
authors.lastname: Hamelin
authors.forename: E
authors.initials: E
authors.lastname: Lecorche
authors.forename: M A
authors.initials: MA
authors.lastname: Bejarano
authors.forename: P
authors.initials: P
authors.lastname: Innominato
authors.forename: M
authors.initials: M
authors.lastname: Sebagh
authors.forename: R
authors.initials: R
authors.lastname: Adam
authors.forename: J F
authors.initials: JF
authors.lastname: Morère
authors.forename: A
authors.initials: A
authors.lastname: Lemoine
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics; D005838:Genotype; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000556:secondary*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D015999:Multivariate Analysis; D009154:Mutation; D009362:Neoplasm Metastasis; D015995:Prevalence; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D012044:Regression Analysis; D015398:Signal Transduction
chemical_list: C117307:KRAS protein, human; D008565:Membrane Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)