Bowel cancer “melted away” after immunotherapy, then stayed away — SkimNews
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- NEOPRISM-CRC trial followed 32 patients with stage 2 or 3 MMR deficient/MSI-high bowel cancer who took pembrolizumab for up to nine weeks before surgery instead of receiving post-operative chemo, and recorded zero cancer recurrences after 33 months.
- By contrast, approximately 25% of patients treated with the standard surgery-plus-chemotherapy approach are expected to relapse within three years, according to figures cited by the UCL-led team.
- Earlier NEOPRISM-CRC data showed 59% of patients had no detectable signs of disease after the nine-week pembrolizumab course, and even those with residual traces after treatment saw no growth or spread during follow-up.
- NEOPRISM-CRC researchers developed personalized blood tests tracking tumor DNA in the bloodstream, finding that disappearance of circulating tumor DNA was strongly associated with no cancer remaining.
- The trial enrolled a narrow patient subset — roughly 10-15% of stage 2 or 3 bowel cancer cases have the MMR deficient/MSI-high genetic profile, equating to 2,000-3,000 UK diagnoses per year.
- UCLH patient Christopher Burston, 73, of Portland, Dorset, was diagnosed with stage 3 bowel cancer in February 2023, received three doses of pembrolizumab over nine weeks, and was told after his May 2023 surgery that 'the cancer had melted away'; he remains cancer-free more than three years later.
- The findings will be presented at the American Association for Cancer Research Annual Meeting 2026 in San Diego, with translational work carried out by UCL and biotechnology company Personalis.
Why it matters: For the 2,000-3,000 UK patients diagnosed annually with MMR deficient/MSI-high stage 2 or 3 bowel cancer, the NEOPRISM-CRC data show pre-surgical pembrolizumab yielded zero recurrences over 33 months versus an expected ~25% relapse rate under standard care, and the personalized blood tests now offer a way to identify responders early.
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