Circulating Cell-Free DNA Levels in Patients with Metastatic Renal Cell Carcinoma.

Limited data about biomarkers are available to predict the outcomes of targeted therapy in metastatic renal cell carcinoma (mRCC). Circulating cell-free DNA (CFD) is elevated in various cancers. We performed a prospective study of patients with mRCC who received targeted therapy in the Soroka Medical Center between 2013 and 2015. CFD levels were measured using a simple fluorometric assay. Blood samples for CFD were collected before treatment and at weeks 1, 4, 12, 18, and 24 of treatment. The normal cut-off level of CFD was defined as 800 ng/ml. The association of CFD with objective response, progression-free survival (PFS), and overall survival was tested, with adjustment for known confounding risk factors. A total of 23 patients were included; 18 were treated with first-line therapy and 5 with second- and third-line therapies. Patients with normal pretreatment CFD level had a better PFS versus patients with increased levels (p = 0.023). In multivariate analysis, factors associated with PFS were pretreatment CFD levels (p = 0.020) and Heng risk (p = 0.006). Elevated pretreatment CFD levels measured using a simple fluorometric assay may be associated with a worse PFS in patients with mRCC. A larger prospective study is warranted in order to validate our observation.