Dynamic ctDNA Changes Are Prognostic of Outcomes in Advanced Melanoma

In a multi-institutional retrospective analysis, Vincent Ma, MD, associate professor in the Department of Medicine at the University of Wisconsin School of Medicine and Public Health, and his colleagues investigated the prognostic utility of circulating tumor DNA (ctDNA) for patients with unresectable stage III or stage IV melanoma. The study specifically focused on 117 patients undergoing treatment with anti–PD-1-based immune checkpoint inhibitor therapy. Utilizing the Signatera tumor-informed ctDNA assay, the research team measured levels at baseline and again at a critical early interval of 3 to 4 weeks after the start of treatment, but prior to the second dose.

Methodology and Patient Categorization

The researchers categorized the cohort based on early ctDNA dynamics. Patients were grouped by whether their ctDNA levels decreased (including those with zero change) or increased relative to their baseline measurements. These dynamics were then correlated with several clinical endpoints, including objective response rate, disease control rate, progression-free survival, and overall survival, as well as long-term kinetics and early ctDNA clearance.

Compelling Clinical Findings

The study’s results revealed that early changes in ctDNA are highly predictive of clinical success. Patients who showed a decrease in ctDNA as early as 3 to 4 weeks post-treatment demonstrated a 30-fold higher odds of achieving disease control and a 23-fold higher odds of an objective response. Furthermore, this molecular response was associated with an 82% reduction in the risk of progression and a 72% reduction in the risk of death.

Conversely, patients whose ctDNA levels increased during this early window faced poor prognoses, with a median PFS of only 2.3 months. Ma highlighted that early ctDNA clearance was a particularly strong indicator of favorable outcomes; patients achieving complete clearance during the early transition saw a 1-year overall survival rate exceeding 90%.

The Importance of Dynamics over Baseline

A key takeaway from the analysis was that baseline ctDNA levels alone were not significantly predictive or prognostic. The study underscores that the dynamic movement of these biomarkers, rather than a single static measurement, is the essential factor for clinicians to monitor when prognosticating outcomes for melanoma patients on immunotherapy.