A Phase I study published in Clinical Cancer Research showed that Personalis’ NeXT Personal MRD assay — a tumor‑informed, whole‑genome sequencing ctDNA test — accurately predicted immunotherapy responses across multiple metastatic solid tumor types. In the cohorts analyzed, an approximate 30% drop in ctDNA before cycle two correlated with improved progression‑free and overall survival; ctDNA clearance was linked to a threefold increase in PFS. Investigators highlighted early ctDNA monitoring as crucial: many patients progressed by conventional assessment timepoints that ctDNA had already signaled. The data suggest tumor‑informed MRD assays can serve as early response biomarkers and potentially distinguish true progression from pseudoprogression. The results support broader use of high‑sensitivity ctDNA assays for treatment decision‑making and trial enrichment; commercial uptake will depend on validation in larger, prospective cohorts and integration into clinical workflows.