Researchers at the Johns Hopkins Kimmel Cancer Center and its Bloomberg~Kimmel Institute for Cancer Immunotherapy determined that liquid biopsy—a blood test that detects circulating tumor DNA (ctDNA)—can predict, within a few weeks, whether patients with advanced non-small cell lung cancer are benefiting from immunotherapy. This finding has the potential to facilitate early treatment decisions, allowing physicians to change therapies unlikely to benefit patients months sooner than is currently possible with standard imaging.