MENLO PARK, Calif. — October 7, 2026
BillionToOne, Inc. announced the publication of a new peer-reviewed head-to-head study evaluating its Northstar Response® assay against a commercially available tumor-informed circulating tumor DNA (ctDNA) assay for monitoring cancer treatment. Published in The Journal of Liquid Biopsy, the retrospective real-world study found that Northstar Response tracked disease dynamics on par with or better than the tumor-informed comparator, without requiring tumor tissue sequencing. The study evaluated 169 paired samples from 61 patients with advanced cancer undergoing treatment, including 71 samples from 36 patients with sequential concurrent blood draws performed within seven days of each other. Following patient-specific baseline normalization, quantitative measurements from the two approaches demonstrated a strong alignment across repeated measurements, with a conditional R² of 0.97. BillionToOne said the findings provide clinical evidence supporting a tissue-free approach for longitudinal molecular monitoring of treatment response.
Northstar Response Shows Strong Agreement With Comparator
The study found that Northstar Response and the tumor-informed assay reached the same conclusion regarding the direction of tumor burden change in 94% of evaluable sequential comparisons, corresponding to 67 of 71 paired measurements. The comparison is significant because tumor-informed assays generally depend on sequencing an earlier tumor tissue sample to identify patient-specific alterations that are subsequently monitored through blood testing. Northstar Response instead uses a tissue-free, methylation-based liquid biopsy approach designed to measure circulating tumor DNA directly from blood. BillionToOne reported that all divergent cases between the two assays were concordant with the available clinical ground truth established through imaging and/or biopsy. According to the company, the findings indicated that the tumor-informed assay produced either false-positive or false-negative results in those cases. The study also included examples in which Northstar Response detected disease progression after tumor biology had changed during treatment, including a case involving hormone receptor conversion in advanced breast cancer.
Tissue-Free Monitoring Captures Tumor Evolution
Northstar Response is designed to monitor changing tumor biology without dependence on a previous tissue biopsy. Because the assay is not restricted to genomic alterations selected from an earlier tissue sample, it can potentially capture clinically meaningful changes that emerge as tumors evolve under treatment pressure. This capability may be particularly relevant in advanced cancer, where repeat tissue biopsies can be difficult, inadequate or unavailable. BillionToOne said the tissue-free workflow may also shorten the time required to initiate molecular treatment monitoring, potentially by weeks, by eliminating the need to obtain and sequence tumor tissue before testing. The study therefore highlights a potential advantage of tumor-agnostic ctDNA monitoring: maintaining the ability to assess changing tumor burden and disease evolution through serial blood samples while avoiding tissue-dependent assay preparation. The company said the findings support the use of standardized liquid biopsy testing as a practical approach for longitudinal cancer monitoring.
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BillionToOne Advances Molecular Diagnostics Platform
Northstar Response is BillionToOne’s tissue-free, methylation-based ctDNA assay developed specifically for treatment response monitoring in cancer patients. The assay uses the company’s patented QCT™ molecular counting technology to quantify tumor burden through serial blood draws without requiring tumor tissue at any stage of the patient journey. BillionToOne’s broader molecular diagnostics platform is based on single-molecule next-generation sequencing and Quantitative Counting Templates™, which are designed to enable precise measurement of disease-associated DNA fragments. The new peer-reviewed study strengthens the clinical evidence supporting Northstar Response as the company advances its approach to accessible, tissue-free molecular monitoring. With strong agreement against a tumor-informed comparator and additional evidence from divergent cases supported by imaging or biopsy, BillionToOne is positioning Northstar Response as a potential option for clinicians seeking reliable and practical assessment of treatment response and tumor evolution.
Source::BillionToOne, press release
