Circulating Tumor DNA Used to Identify Recurrence, Targetable Variants in Late-Stage Melanoma

In a new study appearing in the Journal of Molecular Diagnostics, researchers from the University of Queensland and elsewhere demonstrate that circulating tumor DNA could be used to both identify disease recurrence and identify targetable variants in patients with late-stage melanoma. The researchers analyzed 150 plasma samples obtained from 106 patients with stage III/IV melanoma — 98 of whom were BRAF wildtype and eight of whom had confirmed V600E/K mutations — using a 77-gene CAPP-seq pan-cancer panel. Eighty-five percent of patients, they found, had a detectable variant in a targetable pathway, such as VEGFR, EGFR, and more. However, of the eight patients expected to have a BRAF variant, four had no detectable variant in their blood sample, while BRAF variants were identified in three patients for whom they were not detected in tissue analysis. At the same time, the researchers found patients with low ctDNA concentrations had better disease-specific and progression-free survival, while those with higher ctDNA had worse outcomes. Changes in ctDNA over time also largely tracked with CT scan-gauged response to immune checkpoint inhibitor therapy. "This study demonstrates the value of ctDNA in stage IV melanoma patients as a tool to detect somatic variants with clinically targetable mutations; as a prognostic indicator in stage IV patients; and as a tool for tracking treatment response to ICI," the researchers write in their paper.