title: Increased detection sensitivity for KRAS mutations enhances the prediction of anti-EGFR monoclonal antibody resistance in metastatic colorectal cancer.
abstract: OBJECTIVE
  KRAS mutations represent the main cause of resistance to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs) in metastatic colorectal cancer (mCRC). We evaluated whether highly sensitive methods for KRAS investigation improve the accuracy of predictions of anti-EGFR MoAbs efficacy.
  
  
  METHODS
  We retrospectively evaluated objective tumor responses in mCRC patients treated with cetuximab or panitumumab. KRAS codons 12 and 13 were examined by direct sequencing, MALDI-TOF MS, mutant-enriched PCR, and engineered mutant-enriched PCR, which have a sensitivity of 20%, 10%, 0.1%, and 0.1%, respectively. In addition, we analyzed KRAS codon 61, BRAF, and PIK3CA by direct sequencing and PTEN expression by immunohistochemistry.
  
  
  RESULTS
  In total, 111 patients were considered. Direct sequencing revealed mutations in codons 12 and 13 of KRAS in 43/111 patients (39%) and BRAF mutations in 9/111 (8%), with almost all of these occurring in nonresponder patients. Using highly sensitive methods, we identified up to 13 additional KRAS mutations compared with direct sequencing, all occurring in nonresponders. By analyzing PIK3CA and PTEN, we found that of these 13 patients, 7 did not show any additional alteration in the PI3K pathway.
  
  
  CONCLUSIONS
  The application of highly sensitive methods for the detection of KRAS mutations significantly improves the identification of mCRC patients resistant to anti-EGFR MoAbs.
authors.affiliation: Institute of Pathology, Locarno, Switzerland.
authors.forename: Francesca
authors.initials: F
authors.lastname: Molinari
authors.forename: Lara
authors.initials: L
authors.lastname: Felicioni
authors.forename: Michela
authors.initials: M
authors.lastname: Buscarino
authors.forename: Sara
authors.initials: S
authors.lastname: De Dosso
authors.forename: Fiamma
authors.initials: F
authors.lastname: Buttitta
authors.forename: Sara
authors.initials: S
authors.lastname: Malatesta
authors.forename: Alessandra
authors.initials: A
authors.lastname: Movilia
authors.forename: Marco
authors.initials: M
authors.lastname: Luoni
authors.forename: Renzo
authors.initials: R
authors.lastname: Boldorini
authors.forename: Oscar
authors.initials: O
authors.lastname: Alabiso
authors.forename: Salvatore
authors.initials: S
authors.lastname: Girlando
authors.forename: Barbara
authors.initials: B
authors.lastname: Soini
authors.forename: Alessandra
authors.initials: A
authors.lastname: Spitale
authors.forename: Federica
authors.initials: F
authors.lastname: Di Nicolantonio
authors.forename: Piercarlo
authors.initials: P
authors.lastname: Saletti
authors.forename: Stefano
authors.initials: S
authors.lastname: Crippa
authors.forename: Luca
authors.initials: L
authors.lastname: Mazzucchelli
authors.forename: Antonio
authors.initials: A
authors.lastname: Marchetti
authors.forename: Alberto
authors.initials: A
authors.lastname: Bardelli
authors.forename: Milo
authors.initials: M
authors.lastname: Frattini
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001483:Base Sequence; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000188:drug therapy* / Q000473:pathology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D009362:Neoplasm Metastasis; D051059:PTEN Phosphohydrolase / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D018631:ras Proteins / Q000235:genetics*
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; D066246:ErbB Receptors; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins