Study authors Akhil Chawla, MD, clinical associate professor of Surgery, and Qiang Zhang, MD, PhD in the lab.
Study authors Akhil Chawla, MD, clinical associate professor of Surgery, and Qiang Zhang, MD, PhD, research professor of Medicine in the Division of Hematology and Oncology, in their lab.

June 2026

ONCOLOGY

LIQUID BIOPSY SPOTS HIDDEN PANCREATIC CANCER AFTER TREATMENT

Featuring: Akhil Chawla, MD
Northwestern Medicine scientists have demonstrated that digital droplet PCR (ddPCR) can detect traces of pancreatic cancer missed by conventional next-generation sequencing (NGS) tests. This test could help physicians identify patients whose disease is more likely to return — even when scans appear reassuring. The study findings were published in Clinical Cancer Research,

The sensitive blood test focuses on KRAS, a genetic mutation that drives more than 90% of pancreatic cancers. “As we enter the era of KRAS-targeted therapies, having a screening tool that tracks the same mutation becomes increasingly important,” says senior author Akhil Chawla, MD. It has the potential to change how clinicians identify high-risk patients, how they monitor microscopic disease, and when they intervene.
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​In patients with pancreatic cancer, circulating tumor DNA levels are often very low and hard to detect.
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How the study was conducted
The study followed 106 patients with localized pancreatic cancer from diagnosis through chemotherapy and surgery. At diagnosis, the study found that the more sensitive blood test, ddPCR, detected signs of cancer in nearly four times as many patients as conventional NGS, which are more commonly used. Even after chemotherapy and surgery, ddPCR continued detecting cancer in most patients, while NGS and standard testing didn’t, suggesting that clinicians may be missing residual disease with currently available approaches.

​Better detection meant better prediction of survival outcomes, Chawla’s team found. The clearest example of this was the discovery of a previously hidden group of high-risk patients whose cancer was missed by standard NGS but detected by ddPCR. That group survived a median of 27 months after diagnosis, compared with 41 months among patients who tested negative on both tests.

Searching deeper for KRAS
Liquid biopsies search for traces of DNA shed by cancer cells into the bloodstream. Because these tests rely on a simple blood draw, they can be repeated over time without invasive procedures.

​NGS is more commonly used because it searches for large numbers of cancer-associated genes simultaneously. By contrast, ddPCR searches for one set of genes at a time. In this study, the team used ddPCR to focus on KRAS mutations.

Key findings
The scientists collected blood samples from the study participants (all enrolled in a larger clinical trial) before treatment, after chemotherapy and after surgery between October 2020 and October 2024.
  • At diagnosis, ddPCR detected tumor KRAS DNA in 65% of patients, compared with 17% for NGS
  • After chemotherapy, ddPCR detected tumor KRAS DNA in 60% of patients, compared with 5% for NGS
  • After surgery, ddPCR detected tumor KRAS DNA in 56% of patients, compared with 9% for NGS
  • Patients positive on both tests survived for 11 months on average
  • Patients negative on both tests survived for 41 months on average
  • Patients missed by NGS but detected by ddPCR survived for 27 months on average
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Larger multi-center studies need to validate these findings before ddPCR can be used routinely in pancreatic cancer care.

Dr. Chawla is supported by the NIH (grant 1R50CA293523) and Elsa U. Pardee Foundation.
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​This article was originally published in the Feinberg School of Medicine News Center on July 21, 2026.
Akhil Chawla, MD, Vice Chair of Regional Integration in the Department of Surgery, Clinical Assistant Professor of Surgical Oncology

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