title: Clinical relevance of KRAS-mutated subclones detected with picodroplet digital PCR in advanced colorectal cancer treated with anti-EGFR therapy.
abstract: OBJECTIVE
  KRAS mutations are predictive of nonresponse to anti-EGFR therapies in metastatic colorectal cancer (mCRC). However, only 50% of nonmutated patients benefit from them. KRAS-mutated subclonal populations nondetectable by conventional methods have been suggested as the cause of early progression. Molecular analysis technology with high sensitivity and precision is required to test this hypothesis.
  
  
  METHODS
  From two cohorts of patients with mCRC, 136 KRAS, NRAS, and BRAF wild-type tumors with sufficient tumor material to perform highly sensitive picodroplet digital PCR (dPCR) and 41 KRAS-mutated tumors were selected. All these patients were treated by anti-EGFR therapy. dPCR was used for KRAS or BRAF mutation screening and compared with qPCR. Progression-free survival (PFS) and overall survival (OS) were analyzed according to the KRAS-mutated allele fraction.
  
  
  RESULTS
  In addition to the confirmation of the 41 patients with KRAS-mutated tumors, dPCR also identified KRAS mutations in 22 samples considered as KRAS wild-type by qPCR. The fraction of KRAS-mutated allele quantified by dPCR was inversely correlated with anti-EGFR therapy response rate (P < 0.001). In a Cox model, the fraction of KRAS-mutated allele was associated with worse PFS and OS. Patients with less than 1% of mutant KRAS allele have similar PFS and OS than those with wild-type KRAS tumors.
  
  
  CONCLUSIONS
  This study suggests that patients with mCRC with KRAS-mutated subclones (at least those with a KRAS-mutated subclones fraction lower or equal to 1%) had a benefit from anti-EGFR therapies.
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France. Departement of Biology, Hôpital Européen Georges Pompidou, AP-HP, Paris, France. valerie.taly@parisdescartes.fr pierre.laurent-puig@parisdescartes.fr.
authors.forename: Pierre
authors.initials: P
authors.lastname: Laurent-Puig
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France.
authors.forename: Deniz
authors.initials: D
authors.lastname: Pekin
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Normand
authors.affiliation: RainDance Technologies, Billerica, Massachusetts.
authors.forename: Steve K
authors.initials: SK
authors.lastname: Kotsopoulos
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Nizard
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France.
authors.forename: Karla
authors.initials: K
authors.lastname: Perez-Toralla
authors.affiliation: RainDance Technologies, Billerica, Massachusetts.
authors.forename: Rachel
authors.initials: R
authors.lastname: Rowell
authors.affiliation: RainDance Technologies, Billerica, Massachusetts.
authors.forename: Jeff
authors.initials: J
authors.lastname: Olson
authors.affiliation: RainDance Technologies, Billerica, Massachusetts.
authors.forename: Preethi
authors.initials: P
authors.lastname: Srinivasan
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Le Corre
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France.
authors.forename: Thevy
authors.initials: T
authors.lastname: Hor
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France.
authors.forename: Zakaria
authors.initials: Z
authors.lastname: El Harrak
authors.affiliation: RainDance Technologies, Billerica, Massachusetts.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Li
authors.affiliation: RainDance Technologies, Billerica, Massachusetts.
authors.forename: Darren R
authors.initials: DR
authors.lastname: Link
authors.affiliation: Service d'hépatogastroentérologie et de Cancérologie Digestive, CHU de Reims, Hôpital Robert-Debré, Reims, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Bouché
authors.affiliation: Department of Pathology, Hôpital Ambroise Paré, AP-HP, Université de Versailles St Quentin en Yvelines, Boulogne-Billancourt, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Emile
authors.affiliation: Department of Oncology, Hôpital Européen Georges Pompidou, AP-HP, Paris, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Landi
authors.affiliation: Intitut Gustave Roussy, Villejuif, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Boige
authors.affiliation: RainDance Technologies, Billerica, Massachusetts.
authors.forename: J Brian
authors.initials: JB
authors.lastname: Hutchison
authors.affiliation: Université Paris Sorbonne Cité; INSERM UMR-S1147; Centre Universitaire des Saints-Pères, Paris, France. valerie.taly@parisdescartes.fr pierre.laurent-puig@parisdescartes.fr.
authors.forename: Valerie
authors.initials: V
authors.lastname: Taly
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058990:Molecular Targeted Therapy; D009154:Mutation; D009367:Neoplasm Staging; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D019233:Retreatment; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents; C117307:KRAS protein, human; D066246:ErbB Receptors; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras)