Pilot study of circulating tumor cells in early-stage and metastatic uveal melanoma

Nearly 50% of uveal melanoma (UM) patients develop metastatic disease, and there remains no current standard assay for detection of minimal residual disease. We conducted a pilot study to check the feasibility of circulating tumor cell (CTC) detection in UM. We enrolled 40 patients with early or metastatic UM of which 20 patients had early-stage disease, 19 had metastatic disease, and one was not evaluable. At initial blood draw, 36% of patients had detectable CTCs (30% in early-stage vs. 42% in metastatic), which increased to 54% at data cutoff (40% in early-stage vs. 68% in metastatic). Five early-stage patients developed distant metastases, 60% (3/5) had detectable CTCs before radiographic detection of the metastasis. Landmark overall survival (from study enrollment) at 24 months was statistically lower in CTC-positive vs. negative early-stage UM (p < 0.05). Within this small dataset, the presence of CTCs in early-stage UM predicted an increased risk of metastatic disease and was associated with worse outcomes.