Circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) have been recently investigated in several cancer types, but their respective clinical significance remains to be determined. In our prospective study, we compared the detection rate and the prognostic value of these two circulating biomarkers in patients with metastatic uveal melanoma. GNAQ=GNA11 mutations were characterized in archived tumor tissue. Using a highly sensitive and mutation-specific bidirectional pyrophosphorolysisactivated polymerization (bi-PAP) technique, GNAQ c.626A>T, GNAQ c.626A>C and GNA11 c.626A>T copy numbers were quantified in plasma from 12 mL of blood. CTCs were detected at the same time in 7.5 mL of blood by the CellSearchV R technique. Patient characteristics and outcome were prospectively collected. CTCs (1) were detected in 12 of the 40 included patients (30%, range 1-20). Among the 26 patients with known detectable mutations, ctDNA was detected and quantified in 22 (84%, range 4-11,421 copies=mL). CTC count and ctDNA levels were associated with the presence of miliary hepatic metastasis (p 5 0.004 and 0.03, respectively), with metastasis volume (p 5 0.005 and 0.004) and with each other (p < 0.0001). CTC count and ctDNA levels were both strongly associated with progression-free survival (p 5 0.003 and 0.001) and overall survival (p 5 0.0009 and <0.0001). In multivariate analyses, ctDNA appeared to be a better prognostic marker than CTC. In conclusion, ctDNA and CTC are correlated and both have poor prognostic significance. CTC detection can be performed in every patient but, in patients with detectable mutations, ctDNA was more frequently detected than CTC and has possibly more prognostic value.Uveal melanoma is a rare cancer, with a reported incidence of two to eight new cases per million per year in Europe 1 and the United States.2 Specific mutations are found in this particular type of melanoma: >80% of uveal melanoma express mutually exclusive somatic mutations in two paralog proto-oncogenes, GNAQ 3 and GNA11, 4 which encode a-subunits of heterotrimeric G-proteins involved in the MEK-ERK signaling pathway. 5 In both genes, most mutations occur at nucleotide 626 encoding a glutamine at codon 209 (Q209). The presence of these mutations does not influence the risk of metastasis in patients. 4 Uveal melanoma metastases develop mostly in the liver through hematogenous spread of cancer cells. Despite improvement of diagnosis and treatment of the primary eye tumor, there is no effective treatment of metastatic disease; the prognosis of patients with metastatic uveal melanoma is limited, and although a few patients experience extended survival, the median overall survival (OS) following metastases detection is less than 1 year. 6 Circulating tumor cells (CTCs), which are cancer cells detected in patient blood, may correspond to cancer "seeds" that initiate metastatic relapse.7 Over the past two decades, both molecular and cytological detection techniques have

A B S T R A C TCell-free tumor DNA (ctDNA) has the potential to enable non-invasive diagnostic tests for personalized medicine in providing similar molecular information as that derived from invasive tumor biopsies. The histology-independent phase II SHIVA trial matches patients with targeted therapeutics based on previous screening of multiple somatic mutations using metastatic biopsies. To evaluate the utility of ctDNA in this trial, as an ancillary study we performed de novo detection of somatic mutations using plasma DNA compared to metastasis biopsies in 34 patients covering 18 different tumor types, scanning 46 genes and more than 6800 COSMIC mutations with a multiplexed next-generation sequencing panel. In 27 patients, 28 of 29 mutations identified in metastasis biopsies (97%) were detected in matched ctDNA. Among these 27 patients, one additional mutation was found in ctDNA only. In the seven other patients, mutation detection from metastasis biopsy failed due to inadequate biopsy material, but was successful in all plasma DNA samples providing three more potential actionable mutations. These results suggest that ctDNA analysis is a potential alternative and/or replacement to analyses using costly, harmful and lengthy tissue biopsies of metastasis, irrespective of cancer type and metastatic site,

Customized ctDNA detection by ddPCR achieved a 75% detection rate at baseline. During NCT, ctDNA levels decreased quickly and minimal residual disease was not detected after surgery. However, a slow decrease of ctDNA level during NCT was strongly associated with shorter survival.