When Plasma Can’t Find It; Urine Can
Plasma-based liquid biopsy has transformed how we detect and monitor cancer genomically. But it has a quiet blind spot: in patients with low circulating tumour DNA burden, clonal evolution, or treatment-related suppression of ctDNA shedding, plasma assays can return negative, leaving clinicians without the molecular information they need.
For genitourinary cancers: renal, urothelial, and prostatic, there is a biological reason to look elsewhere. Tumour DNA fragments shed proximally into urine, offering a complementary biofluid that may capture what plasma misses.
At 1Cell.ai, in collaboration with Bombay Hospital Mumbai, we investigated whether urine-based liquid biopsy could close that detection gap.
Our Study: Multi-Specimen Genomic Profiling in 23 GU Cancer Patients
We retrospectively performed molecular spectrum analysis in 23 patients with bladder or prostate cancer, analysing both plasma and urine specimens simultaneously using our OncoIndx NGS panel. ctDNA detection was assessed for concordance and discordance across cancer types and sampling timepoints, with urine findings as the primary focus.
What We Found
The results make a compelling case for urine as a frontline complementary biospecimen:
- Plasma alone detected ctDNA positivity in 39.1% of patients (9/23)
- Urine alone detected ctDNA positivity in 17.4% of patients (4/23)
- Combined plasma + urine analysis increased overall ctDNA detection to 56.5% (13/23)– identifying an additional 17.4% of ctDNA-positive cases that plasma testing alone would have missed entirely
This enhanced detection enables earlier molecular identification of relapse and more timely clinical intervention
Why This Matters
For genitourinary cancers; where proximity to the urinary tract means tumour DNA fragments are shed directly into urine- plasma-only testing is an incomplete strategy. This study demonstrates that urine liquid biopsy isn’t just an add-on; it is a clinically meaningful complement that catches real, actionable molecular signals in patients who would otherwise be classified as ctDNA-negative and potentially undertreated or under-monitored.
As a non-invasive, easily repeatable biofluid, urine has the potential to function as a first-line genomic testing strategy in genitourinary cancers, particularly for patients where plasma ctDNA falls below detection thresholds.
This is 1Cell.ai’s first step into urine-based liquid biopsy and the results suggest it won’t be the last.
Presented at the ASCO Annual Meeting 2026 | J Clin Oncol 44, e17133 (2026) | DOI: 10.1200/JCO.2026.44.16_suppl.e17133