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Oncotarget. 2015 Dec 8;6(39):42008-18. doi: 10.18632/oncotarget.5788.

Circulating tumor DNA to monitor treatment response and detect acquired resistance in patients with metastatic melanoma.

Author information

1
School of Medical Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.
2
Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, New South Wales, Australia.
3
Melanoma Institute Australia, Sydney, New South Wales, Australia.
4
School of Engineering, Edith Cowan University, Joondalup, Western Australia, Australia.
5
Centre for Cancer Research, The University of Sydney at Westmead Millennium Institute, Westmead Hospital, Westmead, New South Wales, Australia.
6
Department of Medical Oncology, Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, New South Wales, Australia.
7
Disciplines of Pathology, The University of Sydney, Sydney, New South Wales, Australia.
8
Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.
9
Department of Medical Oncology, Fiona Stanley Hospital, Murdoch, Western Australia, Australia.
10
School of Medicine and Pharmacology, The University of Western Australia, Crawley, Western Australia, Australia.
11
Medicine, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.
12
School of Pathology and Laboratory Medicine, The University of Western Australia, Crawley, Western Australia, Australia.

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.

KEYWORDS:

MAPK inhibition; acquired resistance; ctDNA; immunotherapy; melanoma

PMID:
26524482
PMCID:
PMC4747205
DOI:
10.18632/oncotarget.5788
[Indexed for MEDLINE]
Free PMC Article

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