Identification of circulating malignant cells and its correlation with prognostic factors and treatment in uveal melanoma. A prospective longitudinal study

Most uveal melanoma patients (UMP) do not show evidence of metastases upon diagnosis. However, despite local tumour control, approximately 50% of them will develop metastases. These findings suggest that malignant cells may have already disseminated by the time of initial diagnosis. The purpose of the study was to detect circulating malignant cells (CMCs) in UMP and to correlate them with prognostic factors and therapy.

Nested reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect CMCs. In each UMP, blood was collected every 3 months. In each visit, 20 RT-PCR tests were performed. The date of diagnosis, largest tumour dimension, type, and date of treatment were obtained.

A total of 30 UMP were enrolled. Five patients were enrolled at the time of diagnosis and 25 patients between 1 and 17 years following diagnosis. No UMP showed clinical evidence of metastasis. A total of 136 visits were registered, 1360 samples collected, and 2720 RT-PCRs performed. CMCs were identified in 29 patients in 119 visits (87.5%). However, in each visit, a low number of positive tests were recorded. CMCs were found in newly diagnosed, irradiated, enucleated, and observed patients regardless of tumour size and time period following treatment.

Uveal melanoma (UM) is not a localized ocular disease. CMCs were recorded at initial diagnosis confirming the early metastatic nature of UM. CMCs were present following treatment, including enucleation, demonstrating that CMCs are capable of disseminating and surviving, possibly as micrometastasis, which would contribute to the pool of CMCs at a later stage. Systemic therapy should be evaluated.