Blood Test Detects Early Nonresponse in Metastatic Prostate Cancer

K., with more than 64,000 men diagnosed and 12,000 deaths each year. For the roughly 10,000 men annually with advanced disease, early assessment of treatment response remains difficult because prostate-specific antigen (PSA) can persist in blood for months. This delay can slow decisions about whether to switch or intensify therapy, underscoring the need for faster response markers. A new study shows that a blood test detecting tumor DNA fragments can identify nonresponse within 6–12 weeks.

University College London (UCL) led a U.K.-wide investigation of a blood-based approach that monitors circulating tumor DNA (ctDNA) alongside serum PSA to track treatment response in advanced prostate cancer. The method analyzes tiny fragments of tumor DNA shed into plasma. Because ctDNA clears rapidly from circulation, it can reveal ongoing tumor growth even when conventional PSA trends show little immediate change.

The study is described as a prospective national cohort and focused on men starting first-line therapy for newly diagnosed metastatic prostate cancer. In total, 117 patients were treated across 14 National Health Service (NHS) centers in the U.K. Blood was evaluated at 6–12 weeks after treatment initiation to determine whether ctDNA remained detectable.

Detectable ctDNA at 6–12 weeks marked a high-risk subgroup. Three in ten men had measurable tumor DNA in blood at that timepoint and showed substantially poorer outcomes, with only half surviving beyond two years, compared with 85% survival among men with undetectable ctDNA. When ctDNA status was combined with PSA, investigators identified a cohort that was 20-fold more likely to die than men with undetectable ctDNA and very low PSA, indicating a strong risk stratification signal.

According to the authors, the approach could allow men whose cancers are not responding to switch or intensify treatment much sooner than current practice. The findings were published in Nature Cancer on May 15, 2026. The study team noted that the same readouts could accelerate clinical research by showing whether new treatments are effective much earlier than standard measures.

"This is so exciting because it's the first time we've ever seen such a clear link between tumor DNA in the blood and outcomes for men with hormone-sensitive advanced cancer. By using it alongside PSA blood tests, we can personalize treatments and help find the right balance between reducing side effects and giving men more time with their loved ones," said Gert Attard, Professor at the UCL Cancer Institute.

"The next step is to show that we can reproduce this and how it can be used in practice. That's why we're implementing it across all our clinical trials for advanced prostate cancer to get the evidence we need to roll this out as soon as possible," added Prof. Attard.

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