The "oncological trace": circulating tumor DNA in uveal melanomas

Background Cell-free DNA (cfDNA) and the tumor DNA it contains can be detected in various body fluids and can be obtained in a minimally invasive manner using a liquid biopsy. The fragmented cell-free tumor DNA (ctDNA) serves as a marker for the presence of tumor cells in the body and its analysis enables genetic tumor characteristics to be determined. For some nonocular tumors ctDNA is already approved as a predictive or prognostic marker. Methods This literature review article describes examples of the use of ctDNA as a biomarker in nonocular tumors and the current status of ctDNA analysis in cases of uveal melanomas. For this purpose, a selective literature search was carried out via PubMed. Results Uveal melanomas are nowadays usually treated by eye-preserving therapy. In these cases, there is usually no tumor tissue available for further diagnostic testing. Alternatively, molecular characteristics of the tumor can be determined by the genetic analysis of ctDNA. In uveal melanomas the presence of ctDNA in the plasma at the time of the primary diagnosis is controversial; however, an increase in the amount of ctDNA, which can be used to investigate diagnostically and prognostically relevant genetic changes, was detected during irradiation therapy of the primary tumor in some patients. In the later course of the disease, the amount of ctDNA in the plasma is a suitable marker for metastatic progression. In some cases, an increase in ctDNA levels could be recognized several months before the clinical detection of metastases. Conclusion The analysis of cfDNA in patients with a uveal melanoma is a promising and minimally invasive method for obtaining information about the tumor or the course of the disease. It is currently being investigated which patients could benefit from it in the future. Several issues related to standardization and technical validation must be addressed for its routine clinical application.