A Phase I study published in Clinical Cancer Research found that Personalis’ tumor‑informed whole‑genome ctDNA assay (NeXT Personal) predicts immunotherapy outcomes across metastatic solid tumors. Investigators showed that a ~30% decline in ctDNA levels before cycle 2 correlated with improved progression‑free and overall survival; ctDNA clearance tripled median PFS in the study cohorts. The analysis included longitudinal plasma sampling across 24 tumor types and linked early ctDNA dynamics to treatment benefit and to distinguishing true progression from pseudoprogression. The data reinforce ctDNA as an early, broadly applicable pharmacodynamic biomarker and could influence how oncologists monitor immune checkpoint responses and make early treatment decisions.