ctDNA Dynamics Identifies Pseudoprogression in a Metastatic Melanoma Patient Treated With Nivolumab/Relatlimab.

Pseudoprogression is known to occur in patients with metastatic melanoma treated with immune checkpoint inhibitors and complicates clinical decision-making. Better methods of distinguishing pseudoprogression from true progression are necessary. In this case report, we show how circulating tumor DNA (ctDNA) plays a role in identifying pseudoprogression on early interval radiologic response assessment in a patient with metastatic melanoma treated with combination anti-programmed cell death protein 1 (anti-PD-1) and anti-lymphocyte activation gene 3 (anti-LAG-3). Circulating tumor DNA is a promising biomarker that has potential to reliably assess response to immune checkpoint inhibitors in melanoma, even when the radiologic findings are misleading or indeterminate. Further research is warranted to identify rates of pseudoprogression across various immune checkpoint inhibitor regimens and to identify the role of ctDNA dynamics to identify this phenomenon.