March 11, 2026 | When surgeons remove a solid tumor, they place a small drain in the resulting cavity to draw off lymphatic fluid that collects there; whatever comes out is simply thrown away. But what is really being poured down the drain?
That’s what Dr. Jose P. Zevallos, Chair of Otolaryngology at University of Pittsburgh Medical Center, asked. The resulting startup, Droplet Bioscience, founded in 2021, has built a Clinical Laboratory Improvements Amendments (CLIA) validated clinical test that analyzes this once-discarded fluid for circulating tumor DNA.
“Post-surgical lymphatic fluid is a really rich source of tumor-associated biomarkers,” says Wendy Winckler, Chief Scientific Officer of Droplet Biosciences
Minimal residual disease (MRD) tests seek to find microscopic evidence of disease: a rogue cluster of cells hiding in a lymph node, for example. Droplet’s test can detect those stragglers in lymphatic fluid 24 hours after surgery, returning results in seven to ten business days and putting molecular data in a physician’s hands before the critical window for adjuvant therapy closes.
“We’re working at one of the most critical inflection points in a patient’s cancer journey … that adjuvant therapy decision,” Winckler explained.
Droplet’s NGS test is tumor-informed. Before or after surgery, a sample of tumor tissue is collected and sequenced to identify the tumor’s specific cancer mutations. Technicians then look for those exact mutations in the post-surgical lymph fluid.
Because healthy lymphatic fluid should contain none of those variants, any match is a red flag. “They would only occur if tumor was still growing,” Winckler said. Noise from the surgery itself—inflammatory debris, bacterial DNA from minor wound contamination—is effectively invisible to the assay, filtered out because the test is hunting for a specific molecular fingerprint.
The lymph fluid is collected roughly 24 hours post-surgery, a window chosen deliberately. The half-life of cell-free DNA is as short as 30 minutes, so waiting a day allows surgical debris to dissipate while still capturing evidence of any persisting disease, Winckler explains. In head-and-neck cases, Droplet’s first and currently only commercially available test, patients are typically hospitalized for three to five days so collection can easily happen in the hospital while the drain is still in place before discharge.
Racing the Clock for Adjuvant Precision
Standard blood-based MRD tests are typically ordered four to six weeks after surgery. By then, according to Winckler, the window for using that information to choose a treatment direction has often already closed. Clinical guidelines generally call for adjuvant therapy—radiation, chemotherapy, or immunotherapy given after surgery to mop up residual disease—to begin within three to four weeks post-operation.
“If there’s a concern that … this is a patient who’s going to relapse, treating early, the data shows, matters,” Winckler explained. “If you don’t even draw your blood until four to six weeks, you’re already after adjuvant has started.”
Plasma-based liquid biopsy tests are a great way to monitor how a patient’s doing on therapy, she continued, but they can’t help you decide which therapy to give. A patient with a positive residual disease finding would benefit from more aggressive adjuvant treatment. A patient on the borderline with a negative result might simply be monitored instead. In both cases, the decision is grounded in molecular evidence rather than clinical guesswork.
Gigabytes of Data, Days Shaved Off
Droplet’s current turnaround time has required more than biological ingenuity. The test analyzes three separate biological samples per patient—tumor tissue, blood (as a control), and the lymph drain fluid—each sequenced to extraordinary depth across 700 genes resulting in 5000x coverage after deduplication with raw coverage typically over 10000x. The resulting files run to hundreds of gigabytes.
On Droplet’s original informatics pipeline, built on a CPU-only environment, data processing alone took more than five days, sometimes approaching ten from receipt of the last sample. But the company’s head of informatics, attending the NVIDIA GCT conference virtually in 2024, encountered the company’s Parabricks GPU-enabled NGS software suite and recognized a solution.
After joining NVIDIA’s Inception startup program, Droplet integrated Parabricks into its CLIA-certified laboratory workflow and is using the Parabricks FQ2BAM (fastq2bam) step to speed up alignment. For analyzing unique molecular identifiers (UMIs), the team is working to implement the Parabricks version of fgbio, developed by Fulcrum Genomics, for UMI processing. Variant calling happens with mutectcaller.
The cumulative results are dramatic: analysis time for the core pipeline steps dropped from five days to roughly one, enabling the company to consistently hit its seven-to-ten-day result window. The speed saved costs as well. The company reports a 30% reduction in total computation cost.
The collaboration is continuing. Droplet is working with NVIDIA to accelerate a proprietary component of its pipeline: a base error model that distinguishes true cancer mutations from sequencing artifacts. Because next-generation sequencing produces noise at a measurable rate, that statistical model is critical to pushing the test’s sensitivity toward its theoretical limit.
Expanding Beyond Head and Neck
Droplet’s commercial test is currently CLIA validated for head-and-neck cancer, but the company is already building proof-of-concept data for two additional indications, driven by common drain types that will facilitate lymph collection. Head-and-neck cancer uses a subcutaneous drain, lung cancer uses thoracic chest tube drains, and muscle-invasive bladder cancer uses abdominal drains. Early feasibility results, while limited in sample size, show that circulating tumor DNA can be detected in post-surgical drain fluid from those cancers as well.
“We do believe that this approach is going to be applicable to all solid tumors that are treated surgically,” Winckler said. The logic is straightforward: wherever surgeons currently place drains, Droplet sees an opportunity.