Author(s): Pauline Zaenker, Leslie Calapre, Michael Clark, Gabriela Marsavela, Carlos Aya-Bonilla, Dr Elin Gray, and Prof Mel Ziman, the School of Medical and Health Sciences, Edith Cowan University, Joondalup, Perth, WA, Australia. Michael Clark and Prof Mel Ziman are also part of the School of Biomedical Science, The University of Western Australia, Crawley, WA, Australia. DermNet NZ Editor in Chief: Adjunct A/Professor Amanda Oakley. Copy edited by Gus Mitchell. July 2018.
Cutaneous melanoma is generally first suspected during a skin check and the diagnosis is confirmed by a positive skin biopsy. Over the last few decades, techniques such as dermoscopy and total body photography have improved melanoma diagnosis and surveillance. However, melanoma detection remains challenging .
At later stages of the cancer, PET or CT scans may be used to follow disease progression.
Blood-based melanoma detection is the detection of melanoma-derived components in the patient’s blood. Blood-based melanoma detection may prove particularly useful for diagnosis, prognosis or surveillance where the primary melanoma is inaccessible or where there are numerous secondary growths (metastases).
Blood-based cancer detection is also known as liquid biopsy.
Blood-based biomarkers related to cancer include:
Figure 1. Tumour biomarkers released into the peripheral bloodstream. Cell-free DNA (cfDNA) and exosomes are released by non-neoplastic tissue while circulating tumour cells, tumour-derived exosomes and tumour-derived exosomes are released by tumours. White blood cells that infiltrate the tumour enable the production of autoantibodies that target the tumour tissue. These markers, along with red blood cells and white blood cells, are found in the blood. Image created by Gabriela Marsavela using resources obtained from somersault18:24.
Blood-based melanoma detection is experimental and currently not in clinical use.
Research into this field is advancing worldwide, and several blood-based melanoma detection and surveillance tests are expected to become available to clinics in the next few years.
Blood-based melanoma detection tests are expected to serve as complementary to current practices, such as skin checks, radiological imaging and pathological tumour tissue testing for melanoma, until the validity and reliability of the new tests are established in large numbers of patients. At this stage, blood-based melanoma detection will not influence treatment until the benefit of the tests are proven and validated.
A small number of tests are used for the diagnosis and monitoring of other cancers.
Depending on the suspected stage of the melanoma, different tests may be used to detect a particular biomarker in the blood (figure 1).
Autoantibodies are antibodies produced by the patient’s own immune system in response to antigens (proteins) that normally reside within the body.
Using a large cohort of 104 patients with early-stage melanoma and 105 healthy volunteers, the melanoma research team at Edith Cowan University in Perth, Australia, has recently identified 139 autoantibodies with the potential to aid in primary melanoma diagnosis. The team are currently developing a blood-based melanoma detection test that uses a combination of 10 of these autoantibodies that may detect the cancer with 81.5% overall accuracy.
CTCs are single tumour cells that shed into the bloodstream, with the potential to seed new tumours (metastases) in distant tissues and organs, which is the main cause of death in cancer patients [9,10].
Many patients develop resistance to melanoma therapies and new drugs are constantly being trialled. Human CTCs may be used to test the efficacy of drugs either in vitro or in mice, as exemplified in a recent study from Cancer Research UK .
Plasma-derived ctDNA are short DNA fragments that are released into the patient's circulation by dying tumour cells.
Clinical trials are required to define the benefits of ctDNA-guided clinical decisions before plasma ctDNA can be used routinely in the management of melanoma.
Exosomes are small vesicles 50–100 nm in diameter produced by all cells in the body. TEXs are currently being researched as potential biomarkers in multiple cancers [24–27]. Current work in melanoma exosomes is limited.
Blood collection and processing are routine procedures performed by most hospitals and pathology laboratories.
Any insights gathered from the research into blood-based melanoma detection could inform the development of similar tests for other cancers.
Complex, time-consuming and expensive research is needed before blood-based melanoma detection can be used in routine clinical practice.
The side effects and risks of blood-based melanoma detection may include:
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