Medical Oncologist
CION Cancer Clinics
When is immunotherapy an option for colon cancer? | CION Cancer Clinics
Immunotherapy is an option mainly when the colon cancer is MSI-high, also called dMMR, a result that comes from testing the tumour tissue. Most colon cancers are not MSI-high, and for them immunotherapy alone rarely helps. This page explains who is eligible, how doctors check, where immunotherapy fits among the other treatments, and the questions to ask if your report does not mention the test at all. At CION Cancer Clinics, a multidisciplinary team plans colon cancer treatment for your stage, from surgery to chemotherapy and follow-up.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed October 2026, next review due October 2027
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The short answer
Who can have immunotherapy for colon cancer?
Immunotherapy is an option mainly for one group: people whose colon cancer is MSI-high, also called dMMR. Those words mean the tumour has lost its system for fixing copying mistakes. Most colon cancers are not like this, and for them immunotherapy on its own rarely helps.
Why one test result matters so much
When a tumour cannot repair its own mistakes, it piles up a very large number of faults. Those faults produce abnormal proteins that make it look foreign to the immune system. Immunotherapy drugs called checkpoint inhibitors take the brakes off the immune system, so it can attack cells it was already able to see. A tumour without that mismatch repair fault gives the immune system far less to see.
Where it is used today
For MSI-high colon cancer that has spread, immunotherapy can now be the first treatment, sometimes in place of chemotherapy. It can also be used later, after chemotherapy has stopped working. For earlier-stage MSI-high cancer, immunotherapy before or after surgery is being studied, and your oncologist will tell you whether that applies to you. The drugs themselves are explained on our page on immunotherapy for MSI-high colorectal cancer.
Why it is not offered to everyone
Immunotherapy is not a stronger version of chemotherapy. Given to a cancer it cannot act on, it brings the side effects and the cost without the benefit, and it delays medicines that would have worked. That is why doctors insist on the test result before they discuss it.
The deciding question is not your stage or your age. It is what the tumour tissue shows.Four different situations
Does immunotherapy work for every type of colon cancer?
No. The same drug can be the most useful treatment for one person and of little use to the next. These are the four situations your oncologist is sorting you into.
MSI-high cancer that has spread
This is the clearest case. Immunotherapy is a standard choice here, either as the first treatment or after chemotherapy. Many people respond, and some responses last a long time, though not everyone responds.
Usually means
- A dMMR or MSI-high result on the tissue
- Spread to the liver, lungs or lining of the abdomen
- Well enough to manage regular treatment visits
MSI-high cancer that has not spread
Surgery remains the main treatment. Trials of immunotherapy before or after the operation have reported encouraging results, and in some people the tumour shrank a great deal before surgery. Whether it is offered depends on the stage, the strength of the evidence and access to a trial.
In stage 2, a dMMR result also changes whether chemotherapy after surgery is useful at all.MSS or pMMR cancer, which is most colon cancer
The repair system works, so the tumour carries fewer faults for the immune system to find. Checkpoint inhibitors alone rarely help here. Treatment rests on chemotherapy, targeted therapy and surgery instead.
This is not a weaker cancer or a worse outlook. It is a different cancer with different medicines.Rare results in between
A small number of tumours carry a POLE fault or a very high mutation count without being MSI-high. These are uncommon, and the tumour board weighs them case by case. If standard results leave few options, ask whether wider testing of the tumour was done.
Not sure whether this applies to you?
Ask an oncologistHow eligibility is checked
How do doctors decide whether immunotherapy suits you?
The tissue is tested
Every colon cancer should have mismatch repair testing on the biopsy or surgery specimen. CION arranges it through its diagnostic partners. Our page on why everyone gets MMR testing explains the test.
The stage is confirmed
Scans show whether the cancer has spread and how far. Immunotherapy is used very differently in a cancer confined to the colon and one that has reached the liver.
Your health is weighed
Some conditions make these drugs riskier. An autoimmune illness, an organ transplant or long-term steroid use all need careful discussion before starting.
The tumour board agrees a plan
Medical and surgical oncologists review the result, the scans and your health together. They decide whether immunotherapy comes first, later, or not at all, and whether surgery still has a role.
On your report
What do MSI, dMMR and the other report words mean?
- MMR
- Mismatch repair. The set of proteins that fix copying mistakes when a cell divides. The test checks whether they are present.
- dMMR
- Deficient mismatch repair. One or more repair proteins are missing. This is the result that opens the door to immunotherapy.
- pMMR
- Proficient mismatch repair. All the repair proteins are present, which is the usual finding in colon cancer.
- MSI-high and MSS
- The same question asked through DNA instead of proteins. MSI-high usually matches dMMR. MSS, meaning stable, usually matches pMMR.
- Checkpoint inhibitor
- The type of immunotherapy used in colon cancer. It releases a brake the cancer uses to hide from the immune system.
- Lynch syndrome
- An inherited cause of dMMR. A dMMR result can prompt a referral to genetic counselling for you and your family.
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Did you know
A dMMR result can matter twice. It can open the way to immunotherapy, and it can point to Lynch syndrome, which brothers, sisters and children may want to be tested for.
Being straight with you
What this page cannot tell you
It cannot tell you whether your tumour is MSI-high. Only the test on your tissue can answer that. If your report does not mention MMR, MSI or dMMR, ask whether the test was done, and if not, whether the stored tissue can still be tested.
It cannot predict how you will respond
Even within the MSI-high group, some cancers shrink quickly, some slowly and some not at all. Nobody can tell in advance which you will be, and your oncologist will judge it from scans during treatment. Occasionally a scan looks worse early on before the cancer shrinks, which is why results are read by the team who know your history.
Who this does not apply to
If your tumour is MSS or pMMR, this page mostly does not apply to you, and our page on immunotherapy in MSS colorectal cancer explains why. It also does not cover rectal cancer, where MSI-high tumours are treated on a separate pathway. If the tumour is in the rectum, see the rectal cancer hub.
If you have a report and are unsure what it says, send it to the helpline. A CION oncologist can tell you whether immunotherapy is worth discussing.Questions we are asked
Common questions about immunotherapy in colon cancer
Is immunotherapy better than chemotherapy for colon cancer?
Only for some people. In MSI-high cancer that has spread, immunotherapy can work better than chemotherapy and is often preferred as the first treatment. In MSS cancer, which is most colon cancer, chemotherapy and targeted therapy remain the main medicines and immunotherapy alone rarely helps.
My report says MSS. Is there any immunotherapy for me?
Not as a standard treatment at present. Combinations with other drugs are being tested in trials, and a rare POLE fault can change the picture. Ask your oncologist whether a trial is open, but do not expect immunotherapy to replace chemotherapy for an MSS cancer.
Can immunotherapy be given after surgery?
For most people, the treatment after surgery is chemotherapy, if any is needed. For MSI-high cancer, adding immunotherapy after surgery has been studied with encouraging results. Whether it is offered to you depends on your stage and the latest evidence, so ask the tumour board directly.
Is immunotherapy gentler than chemotherapy?
It feels different, not necessarily gentler. Many people have little hair loss or sickness. But it can inflame the bowel, thyroid, liver, skin or lungs, sometimes months later. Severe or bloody diarrhoea on immunotherapy needs a call to your team the same day, not a home remedy.
How long does immunotherapy continue?
It usually continues while it is working and side effects are manageable, often for a set maximum period agreed at the start. Some people stop earlier because of side effects and still keep the benefit. Your oncologist will review scans regularly and tell you when stopping is reasonable.
Where is immunotherapy given?
Immunotherapy is given as a drip at CION centres, where the team also monitors blood tests and side effects between doses. The tumour board decides the plan first. If surgery or scans are needed, CION arranges them at accredited partner hospitals and diagnostic centres.
Is immunotherapy very expensive?
It is one of the costlier treatments in colon cancer, and the total depends on the drug and how long it continues. Insurance and government schemes treat it differently. Ask for a written estimate that covers the drug, the visits and the scans before you start.
What should I do if MMR testing was never done?
Ask for it. The stored tissue block from your biopsy or surgery can usually still be tested, even years later. Bring your pathology report and the block details to your oncologist, or send them to the CION helpline, and we will tell you how to arrange it.
Your Specialists
Meet CION's colon cancer specialists. Bring your colonoscopy, scan or biopsy report.
Our surgical and medical oncologists plan colon cancer care together: which operation, whether chemotherapy is needed, and the follow-up that comes after.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
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Sources
- American Cancer Society — Immunotherapy for Colorectal Cancer
- National Cancer Institute — Immunotherapy for Cancer
- National Cancer Institute — Colon Cancer Treatment
- NICE — Molecular testing strategies for Lynch syndrome in people with colorectal cancer
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
What MSI-high status means for your outlookWhat the result says beyond the choice of drugUniversal MMR and MSI testingWhy every colon cancer should be tested, and howCost of immunotherapy for MSI-high colon cancerWhat the treatment costs and what schemes coverImmunotherapy for MSI-high and dMMR cancersHow the drugs work and what to expect on treatment
Talk to us
Not sure whether your report says MSI-high?
Send us the pathology report and we will tell you whether immunotherapy is worth discussing, or whether the test still needs to be done. One helpline serves every CION centre.