title: Tumour pharmacodynamics and circulating cell free DNA in patients with refractory colorectal carcinoma treated with regorafenib.
abstract: BACKGROUND
  Regorafenib, a multi-kinase inhibitor, is used in the treatment of patients with metastatic colorectal cancer refractory to standard therapy. However, this benefit was limited to 1.4 months improvement in overall survival, with more than half of patients experiencing grade 3 to 4 adverse events. We aim to elucidate the pharmacodynamic effects of regorafenib in metastatic colorectal cancer and discover potential biomarkers that may predict clinical benefit.
  
  
  METHODS
  Patients with metastatic colorectal adenocarcinoma refractory to standard therapy with tumours amenable to biopsy were eligible for the study. Regorafenib was administered orally at 160 mg daily for 3 out of 4 weeks with tumour assessment every 2 cycles. Metabolic response was assessed by FDG PET-CT scans (pre-treatment and day 15); paired tumour biopsies (pre-treatment and day 21 post-treatment) were sampled for immunohistochemistry and proteomic profiling analyses. Plasma circulating cell free DNA was quantified serially before and after treatment.
  
  
  RESULTS
  There were 2(6%) partial responses out of 35 patients, and 8(23%) patients had stable disease for more than 7 months. Adverse event profile was similar to reported data. Recurrent somatic mutations in K-RAS, PIK3CA and BRAF were detected in plasma circulating cell free DNA in 14 patients; some mutations were not found in archival tumour. Total plasma circulating cell free DNA inversely correlated with progression free survival (PFS), and presence of KRAS mutations associated with shorter PFS. Immunohistochemistry of pre- and post- treatment biopsies showed majority of patients had downregulation of phosphorylated-VEGFR2, podoplanin, phosphorylated-AKT, Ki-67 and upregulation of the MEK-ERK axis, phosphorylated-C-MET, phosphorylated-SRC, phosphorylated-STAT3 and phosphorylated-JUN. Proteomic analysis of fine needle tumour aspirates showed down-regulation of PI3K was associated with longer PFS.
  
  
  CONCLUSIONS
  Plasma circulating cell free DNA may yield potential predictive biomarkers of regorafenib treatment. Downregulation of the PI3K-AKT axis may be an important predictor of clinical benefit.
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Andrea_la_wong@nuhs.edu.sg.
authors.forename: Andrea Li Ann
authors.initials: AL
authors.lastname: Wong
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Joline_sj_lim@nuhs.edu.sg.
authors.forename: Joline Si Jing
authors.initials: JS
authors.lastname: Lim
authors.affiliation: Department of Diagnostic Imaging, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Arvind_kumar_sinha@nuhs.edu.sg.
authors.forename: Arvind
authors.initials: A
authors.lastname: Sinha
authors.affiliation: Department of Diagnostic Imaging, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Anil_gopinathan@nuhs.edu.sg.
authors.forename: Anil
authors.initials: A
authors.lastname: Gopinathan
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Robert_lim@nuhs.edu.sg.
authors.forename: Robert
authors.initials: R
authors.lastname: Lim
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Chee_seng_tan@nuhs.edu.sg.
authors.forename: Chee-Seng
authors.initials: CS
authors.lastname: Tan
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Thomas_soh@nuhs.edu.sg.
authors.forename: Thomas
authors.initials: T
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authors.affiliation: Department of Diagnostic Imaging, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Venkatesh.Sudhakar@mayo.edu.
authors.forename: Sudhakar
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authors.lastname: Venkatesh
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. titince@yahoo.com.
authors.forename: Christina
authors.initials: C
authors.lastname: Titin
authors.affiliation: Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. csinurs@nus.edu.sg.
authors.forename: Nur Sabrina
authors.initials: NS
authors.lastname: Sapari
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. csilsc@nus.edu.sg.|Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. csilsc@nus.edu.sg.
authors.forename: Soo-Chin
authors.initials: SC
authors.lastname: Lee
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. wei_peng_yong@nuhs.edu.sg.|Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. wei_peng_yong@nuhs.edu.sg.
authors.forename: Wei-Peng
authors.initials: WP
authors.lastname: Yong
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. david_sp_tan@nuhs.edu.sg.|Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. david_sp_tan@nuhs.edu.sg.
authors.forename: David Shao Ping
authors.initials: DS
authors.lastname: Tan
authors.affiliation: Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. Brendan_nl_pang@nuhs.edu.sg.|Department of Pathology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Brendan_nl_pang@nuhs.edu.sg.
authors.forename: Brendan
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authors.lastname: Pang
authors.affiliation: Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. csiwtt@nus.edu.sg.
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Wang
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. yingkiat.zee@pcc.sg.
authors.forename: Ying-Kiat
authors.initials: YK
authors.lastname: Zee
authors.affiliation: Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. Richie.soong@nus.edu.sg.|Department of Pathology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. Richie.soong@nus.edu.sg.
authors.forename: Richie
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authors.affiliation: Bayer Healthcare Pharmaceuticals, 100 Bayer Boulevard, PO Box 915, Whippany, NJ, 07981-0915, USA. Zuzana.trnkova@bayer.com.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Trnkova
authors.affiliation: Bayer Healthcare Pharmaceuticals, 100 Bayer Boulevard, PO Box 915, Whippany, NJ, 07981-0915, USA. Chetan.lathia@bayer.com.
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authors.affiliation: Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. csitjp@nus.edu.sg.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Thiery
authors.affiliation: Bayer Healthcare Pharmaceuticals, 100 Bayer Boulevard, PO Box 915, Whippany, NJ, 07981-0915, USA. Scott.Wilhelm@bayer.com.
authors.forename: Scott
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authors.affiliation: Bayer Healthcare Pharmaceuticals, 100 Bayer Boulevard, PO Box 915, Whippany, NJ, 07981-0915, USA. michael.jeffers@bayer.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Jeffers
authors.affiliation: Department of Haematology-Oncology, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore. phcgbc@nus.edu.sg.|Cancer Science Institute, Centre for Translational Medicine, 14 Medical Drive, #12-01, Singapore, 117599, Singapore. phcgbc@nus.edu.sg.
authors.forename: Boon-Cher
authors.initials: BC
authors.lastname: Goh
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D002474:Cell-Free System; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000097:blood* / Q000188:drug therapy*; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000097:blood*; D003710:Demography; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010671:Phenylurea Compounds / Q000009:adverse effects / Q000627:therapeutic use*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D040901:Proteomics; D011725:Pyridines / Q000009:adverse effects / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; D010671:Phenylurea Compounds; D011725:Pyridines; C559147:regorafenib; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human