A Phase I study published in Clinical Cancer Research demonstrated that Personalis’ NeXT Personal whole‑genome, tumor‑informed circulating tumor DNA (ctDNA) assay predicts early immunotherapy response across diverse metastatic solid tumors. Investigators from Spain’s Val d’Hebron Institute of Oncology analyzed ~1,455 longitudinal plasma samples from retrospective (136 patients) and prospective (66 patients) cohorts. Key findings: a ~30% decline in ctDNA before cycle 2 correlated with improved progression‑free and overall survival; ctDNA clearance produced a median threefold increase in PFS; sustained MRD negativity at 180 days associated with 100% overall survival in the study set. Authors highlighted ctDNA monitoring’s ability to distinguish true progression from pseudoprogression. The data support early ctDNA integration into immuno‑oncology decision‑making and underscore the importance of initiating monitoring as soon as treatment begins. The results could influence trial designs and accelerate biomarker‑guided therapy adjustments.