Researchers have been seeking to find a connection between nonspecific biomarkers (things we ALL have circulating in our blood) like LDH, various white blood cells (neutrophils and monocytes - whether as an absolute count or as a neutrophil to lymphocyte ratio), myeloid-derived suppressor cells (MDSCs) and T-regs (See post with links about all that here: Blood markers associated with clinical outcomes). And while many meaningful correlations have been drawn between these components and response to treatment (or lack thereof); the fact that they are all affected by numerous circumstances other than melanoma and its treatment, create limitations in the clarity with which they can be used to PREDICT responses.
With recent scientific advances, PCR testing (Polymerase chain reaction) has become more efficient and cost-effective, allowing labs to copy or "amplify" small segments of DNA or RNA though screening blood or other biological specimens. This ability allows the cellular identification of whatever may be floating in that blood sample....whether it is a virus or fungus, or actual bits and pieces of tumor cells themselves, to allow a determination of disease burden, prognosis, and response to treatment. Here is an earlier post: Circulating tumor cells: how they may eventually impact melanoma diagnosis and evaluation of response
Now there are these reports:
Liquid biopsy utility for the surveillance of cutaneous malignant melanoma patients. Haung and Hoon. Mol Oncol. 2015 Dec 17.
Cutaneous melanoma is one of the highest incident-rate cancers with increasing prevalence in Western societies. Despite the advent of new approved therapeutics, the 5-year overall survival rate of stage IV melanoma patients remains below 15%. Current treatments for late stage disease have shown higher efficacy when treated at a lower disease burden. Thus, blood-based biomarkers capable of detecting melanoma prior to clinically evident distant metastasis, will improve the treatment and outcomes for melanoma patients. To that end, effective treatment of melanoma necessitates identification of patients at risk for developing distant metastases. Furthermore, employing blood biomarkers that monitor cancer progression over the course of treatment is a promising solution to post-treatment drug resistance often developed in melanoma patients. Non-invasive blood biomarker assays allow for regular dynamic monitoring of disease. "Liquid Biopsy" of blood, which exploits circulating tumor cells (CTCs), cell-free circulating tumor DNA (ctDNA) and cell-free circulating microRNA (cmiRNA), has been shown to detect prognostic factors for relapse in AJCC stage III and stage IV melanoma patients. Moreover, molecular characterization of CTC and analysis of various forms of ctDNA present promising potential in development of individualized therapy for melanoma patients. New approaches such as massive parallel sequencing (MPS) provide a comprehensive view of the disease progression, allowing for the selection of therapeutic options for individual patients. With advancements of improving molecular assays, liquid biopsy analysis as a powerful, routine clinical assay for melanoma patients, is highly promising prospective.
Circulating melanoma cells as a potential biomarker to detect metastasis and evaluate prognosis. Hida, Yoneta, Wakamatsu, et al. Australas J Dermatol. 2016 Mar 1.
Then, there's the examination of the properties of the tumor sample itself. This article talks about looking at the tumor in regard to how well it is being recognized by the immune system....specifically t-cells:
Here...the tumor is being characterized by surface molecules that are correlated with prognosis:
Here the tumor is being analyzed for specific genetic variations: