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Immunotherapy before bowel cancer surgery: who benefits?
For a specific group, bowel cancers that are mismatch repair deficient (dMMR), also called MSI-high, a short course of immunotherapy before surgery can shrink or even eliminate the tumour. These cancers make up roughly 10 to 15% of stage two and three bowel cancers. Every bowel cancer in the UK should be tested for this, so ask your team for your result.
What mismatch repair deficiency means
Mismatch repair proteins correct errors when cells copy their DNA. When they are not working, tumours accumulate many mutations. That makes them highly visible to the immune system, and immunotherapy drugs (checkpoint inhibitors) can release the brakes so the immune system attacks them. Some dMMR cancers arise from Lynch syndrome, an inherited condition, so a dMMR result may also lead to genetic testing for you and your family.
What the trials show
| Trial | What was tested | Result |
|---|---|---|
| NEOPRISM-CRC (UK) | Nine weeks of pembrolizumab before surgery in 32 patients with stage 2 or 3 dMMR cancer | 59% had no cancer left at surgery; none had relapsed at nearly three years of follow-up (reported April 2026) |
| NICHE-2 (Netherlands) | Short-course combination immunotherapy before colon cancer surgery | Major tumour response in almost all patients |
| Dostarlimab in dMMR rectal cancer (US) | Immunotherapy alone for locally advanced rectal cancer | Complete clinical response in the initial patients, allowing many to avoid surgery and radiotherapy |
These are small trials with impressive results. Pre-operative immunotherapy for dMMR colon cancer is not yet standard everywhere in the NHS, and access depends on approvals and trials. For dMMR rectal cancer, an immunotherapy-first "watch and wait" approach is increasingly discussed.
What it means for surgery
- Surgery remains standard for most bowel cancers, including most dMMR colon cancers, but it may come after immunotherapy rather than straight away.
- Avoiding chemotherapy: immunotherapy may replace chemotherapy after surgery for some patients.
- Organ preservation: for some dMMR rectal cancers, immunotherapy may avoid the need for an operation and a stoma, with close surveillance.
- Everything is decided at a cancer MDT with oncologists, radiologists, pathologists and surgeons.
Questions to ask your cancer team
- What is my MMR / MSI status?
- If it is deficient, am I eligible for immunotherapy before surgery, or for a trial?
- Should I and my family be tested for Lynch syndrome?
- How would immunotherapy change the timing or extent of my operation?
Mr Papettas works within the colorectal cancer MDT and can discuss how these developments affect your surgical plan. His audited bowel resection outcomes are at bowel resection outcomes.
Common questions
Can immunotherapy replace surgery for bowel cancer?
For some dMMR rectal cancers, immunotherapy alone has produced complete responses, allowing surgery to be avoided with close monitoring. For most colon cancers, surgery is still needed, but immunotherapy may be given first.
How do I know if my cancer is dMMR?
Bowel cancer biopsies in the UK are tested for mismatch repair status. Ask your cancer team for your result.
Does dMMR mean I have Lynch syndrome?
Not necessarily. Many dMMR cancers are sporadic, but some are caused by Lynch syndrome, so further genetic testing is usually offered.
Is pre-operative immunotherapy available on the NHS?
Access is evolving and depends on approvals and clinical trials. Your oncologist can tell you what is currently available to you.
This guide is general information, not personal medical advice. If you have severe abdominal pain, heavy bleeding, a high temperature or vomiting, call 111, or 999 in an emergency.