title: Circulating tumor DNA to monitor treatment response and detect acquired resistance in patients with metastatic melanoma.
abstract: Repeat tumor biopsies to study genomic changes during therapy are difficult, invasive and data are confounded by tumoral heterogeneity. The analysis of circulating tumor DNA (ctDNA) can provide a non-invasive approach to assess prognosis and the genetic evolution of tumors in response to therapy. Mutation-specific droplet digital PCR was used to measure plasma concentrations of oncogenic BRAF and NRAS variants in 48 patients with advanced metastatic melanoma prior to treatment with targeted therapies (vemurafenib, dabrafenib or dabrafenib/trametinib combination) or immunotherapies (ipilimumab, nivolumab or pembrolizumab). Baseline ctDNA levels were evaluated relative to treatment response and progression-free survival (PFS). Tumor-associated ctDNA was detected in the plasma of 35/48 (73%) patients prior to treatment and lower ctDNA levels at this time point were significantly associated with response to treatment and prolonged PFS, irrespective of therapy type. Levels of ctDNA decreased significantly in patients treated with MAPK inhibitors (p < 0.001) in accordance with response to therapy, but this was not apparent in patients receiving immunotherapies. We show that circulating NRAS mutations, known to confer resistance to BRAF inhibitors, were detected in 3 of 7 (43%) patients progressing on kinase inhibitor therapy. Significantly, ctDNA rebound and circulating mutant NRAS preceded radiological detection of progressive disease. Our data demonstrate that ctDNA is a useful biomarker of response to kinase inhibitor therapy and can be used to monitor tumor evolution and detect the early appearance of resistance effectors.
authors.affiliation: School of Medical Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.
authors.forename: Elin S
authors.initials: ES
authors.lastname: Gray
authors.affiliation: Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, New South Wales, Australia.|Melanoma Institute Australia, Sydney, New South Wales, Australia.
authors.forename: Helen
authors.initials: H
authors.lastname: Rizos
authors.affiliation: School of Medical Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Reid
authors.affiliation: Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, New South Wales, Australia.|Melanoma Institute Australia, Sydney, New South Wales, Australia.
authors.forename: Suzanah C
authors.initials: SC
authors.lastname: Boyd
authors.affiliation: School of Medical Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Pereira
authors.affiliation: School of Engineering, Edith Cowan University, Joondalup, Western Australia, Australia.
authors.forename: Johnny
authors.initials: J
authors.lastname: Lo
authors.affiliation: Centre for Cancer Research, The University of Sydney at Westmead Millennium Institute, Westmead Hospital, Westmead, New South Wales, Australia.
authors.forename: Varsha
authors.initials: V
authors.lastname: Tembe
authors.affiliation: School of Medical Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Freeman
authors.affiliation: Centre for Cancer Research, The University of Sydney at Westmead Millennium Institute, Westmead Hospital, Westmead, New South Wales, Australia.|Department of Medical Oncology, Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, New South Wales, Australia.
authors.forename: Jenny H J
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Disciplines of Pathology, The University of Sydney, Sydney, New South Wales, Australia.|Melanoma Institute Australia, Sydney, New South Wales, Australia.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Scolyer
authors.affiliation: Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.
authors.forename: Kelvin
authors.initials: K
authors.lastname: Siew
authors.affiliation: Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.
authors.forename: Chris
authors.initials: C
authors.lastname: Lomma
authors.affiliation: Department of Medical Oncology, Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, New South Wales, Australia.
authors.forename: Adam
authors.initials: A
authors.lastname: Cooper
authors.affiliation: Department of Medical Oncology, Fiona Stanley Hospital, Murdoch, Western Australia, Australia.|School of Medicine and Pharmacology, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Muhammad A
authors.initials: MA
authors.lastname: Khattak
authors.affiliation: Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.|School of Medicine and Pharmacology, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Tarek M
authors.initials: TM
authors.lastname: Meniawy
authors.affiliation: Medicine, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.|Melanoma Institute Australia, Sydney, New South Wales, Australia.
authors.forename: Georgina V
authors.initials: GV
authors.lastname: Long
authors.affiliation: Department of Medical Oncology, Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, New South Wales, Australia.|Melanoma Institute Australia, Sydney, New South Wales, Australia.
authors.forename: Matteo S
authors.initials: MS
authors.lastname: Carlino
authors.affiliation: Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.|School of Medicine and Pharmacology, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Millward
authors.affiliation: School of Medical Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.|School of Pathology and Laboratory Medicine, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Melanie
authors.initials: M
authors.lastname: Ziman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D004273:DNA, Neoplasm / Q000097:blood* / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008545:Melanoma / Q000097:blood* / Q000188:drug therapy* / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D058990:Molecular Targeted Therapy / Q000379:methods; D009154:Mutation; D009362:Neoplasm Metastasis; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000706:statistics & numerical data; D011379:Prognosis; D016016:Proportional Hazards Models; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D055815:Young Adult
chemical_list: D004273:DNA, Neoplasm; D008565:Membrane Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human
keywords: MAPK inhibition; acquired resistance; ctDNA; immunotherapy; melanoma