title: Characterizing the patterns of clonal selection in circulating tumor DNA from patients with colorectal cancer refractory to anti-EGFR treatment.
abstract: BACKGROUND
  KRAS and EGFR ectodomain-acquired mutations in patients with metastatic colorectal cancer (mCRC) have been correlated with acquired resistance to anti-EGFR monoclonal antibodies (mAbs). We investigated the frequency, co-occurrence, and distribution of acquired KRAS and EGFR mutations in patients with mCRC refractory to anti-EGFR mAbs using circulating tumor DNA (ctDNA).
  
  
  METHODS
  Sixty-two post-treatment plasma and 20 matching pretreatment archival tissue samples from KRAS (wt) mCRC patients refractory to anti-EGFR mAbs were evaluated by high-sensitivity emulsion polymerase chain reaction for KRAS codon 12, 13, 61, and 146 and EGFR 492 mutations.
  
  
  RESULTS
  Plasma analyses showed newly detectable EGFR and KRAS mutations in 5/62 [8%; 95% confidence interval (CI) 0.02-0.18] and 27/62 (44%; 95% CI 0.3-0.56) samples, respectively. KRAS codon 61 and 146 mutations were predominant (33% and 11%, respectively), and multiple EGFR and/or KRAS mutations were detected in 11/27 (41%) cases. The percentage of mutant allele reads was inversely correlated with time since last treatment with EGFR mAbs (P = 0.038). In the matching archival tissue, these mutations were detectable as low-allele-frequency clones in 35% of patients with plasma mutations after treatment with anti-EGFR mAbs and correlated with shorter progression-free survival (PFS) compared with the cases with no new mutations (3.0 versus 8.0 months, P = 0.0004).
  
  
  CONCLUSIONS
  Newly detected KRAS and/or EGFR mutations in plasma ctDNA from patients refractory to anti-EGFR treatment appear to derive from rare, pre-existing clones in the primary tumors. These rare clones were associated with shorter PFS in patients receiving anti-EGFR treatment. Multiple simultaneous mutations in KRAS and EGFR in the ctDNA and the decline in allele frequency after discontinuation of anti-EGFR therapy in a subset of patients suggest that several resistance mechanisms can co-exist and that relative clonal burdens may change over time. Monitoring treatment-induced genetic alterations by sequencing ctDNA could identify biomarkers for treatment screening in anti-EGFR-refractory patients.
authors: Department of Gastrointestinal Medical Oncology.
authors: M P
authors: MP
authors: Morelli
authors: Department of Gastrointestinal Medical Oncology.
authors: M J
authors: MJ
authors: Overman
authors: Department of Gastrointestinal Medical Oncology.
authors: A
authors: A
authors: Dasari
authors: Department of Gastrointestinal Medical Oncology.
authors: S M A
authors: SMA
authors: Kazmi
authors: Department of Gastrointestinal Medical Oncology.
authors: T
authors: T
authors: Mazard
authors: Department of Gastrointestinal Medical Oncology; Clinical Cancer Prevention.
authors: E
authors: E
authors: Vilar
authors: Department of Gastrointestinal Medical Oncology.
authors: V K
authors: VK
authors: Morris
authors: Department of Gastrointestinal Medical Oncology.
authors: M S
authors: MS
authors: Lee
authors: Department of Gastrointestinal Medical Oncology.
authors: D
authors: D
authors: Herron
authors: Department of Gastrointestinal Medical Oncology.
authors: C
authors: C
authors: Eng
authors: Investigational Cancer Therapeutics.
authors: J
authors: J
authors: Morris
authors: Department of Gastrointestinal Medical Oncology.
authors: B K
authors: BK
authors: Kee
authors: Biostatistics.
authors: F
authors: F
authors: Janku
authors: Department of Gastrointestinal Medical Oncology.
authors: F L
authors: FL
authors: Deaton
authors: Department of Gastrointestinal Medical Oncology.
authors: C
authors: C
authors: Garrett
authors: Pathology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors: D
authors: D
authors: Maru
authors: Sysmex Inostics, Hamburg, Germany.
authors: F
authors: F
authors: Diehl
authors: Sysmex Inostics, Hamburg, Germany.
authors: P
authors: P
authors: Angenendt
authors: Department of Gastrointestinal Medical Oncology. Electronic address: SKopetz@mdanderson.org.
authors: S
authors: S
authors: Kopetz
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002999:Clone Cells; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000401:mortality / Q000473:pathology*; D004273:DNA, Neoplasm / Q000097:blood / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000097:blood / Q000235:genetics; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D009367:Neoplasm Staging; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000097:blood / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000097:blood / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D012189:Retrospective Studies; D015996:Survival Rate; D018631:ras Proteins / Q000097:blood / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C512478:EGFR protein, human; D066246:ErbB Receptors; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins
keywords: EGFR acquired mutation; KRAS acquired mutation; anti-EGFR mAbs; ctDNA
references: Cancer Biol Ther. 2013 Dec;14(12):1143-6
references: 24025416
references: Cancer Biol Ther. 2020 Oct 2;21(10):891-898
references: 33026965
references: Ann Oncol. 2015 Jan;26(1):13-21
references: 25115304
references: Nature. 2012 Jun 28;486(7404):537-40
references: 22722843
references: Mol Cancer. 2014 May 31;13:135
references: 24885062
references: Nat Methods. 2006 Jul;3(7):551-9
references: 16791214
references: Nat Med. 2012 Jan 22;18(2):221-3
references: 22270724
references: Oncologist. 2008 Dec;13(12):1270-5
references: 19056857
references: Clin Cancer Res. 2011 Jul 15;17(14):4901-14
references: 21632860
references: Sci Transl Med. 2014 Feb 19;6(224):224ra24
references: 24553385
references: Ann Oncol. 2014 Sep;25(9):1729-1735
references: 25009010
references: Nature. 2012 Jun 28;486(7404):532-6
references: 22722830
references: Cancer Biol Ther. 2014 Jun 1;15(6):768-76
references: 24642870
references: JAMA. 2010 Oct 27;304(16):1812-20
references: 20978259
references: Clin Cancer Res. 2013 Dec 15;19(24):6751-65
references: 24122793
references: Ann Oncol. 2014 Sep;25(9):1756-1761
references: 24942275
references: Ann Oncol. 2013 May;24(5):1267-73
references: 23293113
references: J Clin Oncol. 2009 Oct 20;27(30):5068-74
references: 19738126
references: N Engl J Med. 2009 Apr 2;360(14):1408-17
references: 19339720
references: Clin Cancer Res. 2014 Dec 15;20(24):6429-38
references: 24916700
references: Ann Oncol. 2012 Sep;23(9):2313-2318
references: 22396447
references: Radiology. 2012 May;263(2):409-18
references: 22438364
references: Br J Cancer. 2009 Aug 18;101(4):715-21
references: 19603018
references: Cancer Discov. 2013 Jun;3(6):658-73
references: 23729478