A trial of pembrolizumab before surgery for bowel cancer (NEOPRISM-CRC)

Cancer type:

Bowel (colorectal) cancer
Colon cancer
Rectal cancer




Phase 2

This trial is looking to see if having pembrolizumab before surgery improves treatment for bowel cancer that has a high risk of coming back.

It is for people who:

  • are going to have surgery to remove their cancer and 
  • have certain gene changes (mutations Open a glossary item) in their cancer cells    

More about this trial

Most people have surgery for bowel cancer that hasn’t spread. You might also have chemotherapy after surgery.

Doctors are looking for ways to improve treatment for people whose bowel cancer hasn’t spread. In this trial they are looking at having a drug called pembrolizumab before surgery. Pembrolizumab is a type of immunotherapy. It stimulates the body's immune system Open a glossary item to fight cancer cells.

The main aims of the trial are to find out:

  • how safe it is to have pembrolizumab before surgery
  • how well pembrolizumab works to shrink the cancer
  • more about the side effects of treatment

Who can enter

The following bullet points are a summary of the entry conditions for this trial. Talk to your doctor or the trial team if you are unsure about any of these. They will be able to advise you. 

Who can take part

You may be able to join this trial if all of the following apply. You:

  • have adenocarcinoma Open a glossary item of the bowel. This includes rectal cancer if you won’t need to have chemoradiotherapy Open a glossary item before surgery.
  • have cancer that may have spread to nearby lymph nodes Open a glossary item or to surrounding tissue. But it hasn’t spread to distant parts of the body. This is stage 2 to stage 3 cancer.
  • have cancer that is microsatellite instability high (MSI high Open a glossary item) or mismatch repair deficient (MMRd) Open a glossary item. Your doctor will know this.
  • are well enough to have surgery with the aim to cure followed by chemotherapy
  • have satisfactory blood test results
  • are willing to use reliable contraception during the trial and for a period after if there is any chance you or your partner could become pregnant 
  • are at least 18 years old 

Who can’t take part

Cancer related
You cannot join this trial if any of these apply. You:

  • have cancer spread to the brain or spinal cord 
  • have cancer that has spread elsewhere in the body or into the lymph nodes around the abdomen (peritoneum Open a glossary item)
  • are going to have radiotherapy
  • have had pembrolizumab in the past or a similar drug 
  • have had another cancer drug in the 4 weeks before you join the trial
  • have moderate to severe side effects from past treatment that aren’t getting better. You can join if you have hair loss or numbness and tingling in your hands or feet (peripheral neuropathy Open a glossary item).
  • have or had another cancer that could affect the assessments doctors do to check if treatment is working
  • are taking an experimental drug or using a device as part of another clinical trial. This is if it is within 28 days of joining this trial.

Medical conditions
You cannot join this trial if any of these apply. You:

  • have a problem with how your kidneys and liver work
  • have had a severe skin reaction to other drugs that stimulate the immune system
  • have an autoimmune condition Open a glossary item that needs treatment apart from certain ones. Your doctor will know about this.
  • have or had scarring on the lungs or active inflammation of the lungs (pneumonitis Open a glossary item) that needs or needed treatment
  • have HIV, hepatitis C, an active hepatitis B infection, tuberculosis or any other active infection that needs treatment into the bloodstream. You might be able to take part if your hepatitis is controlled with medication. 
  • have had a stem cell transplant with somebody else’s cells (allogeneic transplant Open a glossary item) or you have had an organ transplant Open a glossary item in the past
  • have inflammation of the lining of your tummy or abdomen (peritonitis) because you have developed a hole in your bowel where the cancer is
  • have a blocked bowel and you haven’t had treatment 
  • have a problem with how your immune system works or are having treatment that damps down the immune system. This includes steroids within 7 weeks of starting trial treatment unless it was a low dose.
  • have any other medical condition, mental health problem or a problem with drugs and alcohol that would affect you taking part 

You cannot join this trial if any of these apply. You:

  • are allergic to pembrolizumab or anything it contains
  • have had a live vaccine Open a glossary item within 30 days 
  • are pregnant or breastfeeding

Trial design

This is a phase 2 trial. The team need 32 people to take part. 

Everyone has pembrolizumab followed by surgery. 

You have pembrolizumab in cycles Open a glossary item. Each cycle is 3 weeks. The number of cycles you have depends on the levels of mutations in your cancer cells. Your doctor analyses a sample of cancer tissue to find this out. Having a low level means you probably won’t benefit much from pembrolizumab. 

You have either:

  • 1 cycle of pembrolizumab if you have a low level of mutations or 
  • 3 cycles of pembrolizumab if you have a medium to high level of mutations

You have it as a drip into a vein. It takes about 30 minutes each time. 
You then have surgery about 4 to 6 weeks after finishing pembrolizumab. Taking part in this trial means your surgery is delayed while you have pembrolizumab. This is by about 6 to 13 weeks. 

Your doctor will tell you what surgery involves and how long you will stay in hospital for. 

Samples for research 
The researchers ask you to give some extra tissue samples. They collect these when you have a colonoscopy Open a glossary item and surgery. They also ask to take some extra blood samples. Where possible, you have these at the same time as your routine blood tests.

They plan to use the samples to:

  • see how well pembrolizumab worked before surgery
  • look at genes Open a glossary item to understand more about bowel cancer
  • look for substances called biomarkers Open a glossary item to help work out why treatment might work for some people and not for others

The team ask for 6 poo (stool) samples during the trial. They also ask you to collect 6 samples from your tongue using a swab. The team give you the sample kits to take home with you. They will give you instructions on how to collect the samples and information about how to return them.

Some of the samples are optional. You can say no to them and it won’t affect you taking part in the rest of the trial. 

Quality of life
The trial team ask you to fill out a questionnaire:

  • before you start treatment
  • at set times during treatment
  • at set times after treatment 

The questionnaire asks about side effects and how you’ve been feeling. This is called a quality of life study.

Hospital visits

You see the doctor and have tests before you can take part. These include:

You have pembrolizumab in the day care ward. You have a check up before each dose. 

You see your doctor one month after surgery for a check up. After that you see them:

  • every 3 months in the first year
  • about every 6 months in the second and third years

You have a CT scan or MRI scan before surgery. And then after surgery at the following timepoints:

  • 6 months
  • 12 months
  • 24 months 
  • 36 months

You also have a colonoscopy at 1 year and 3 years after surgery. This is part of your routine care. 

Side effects

The trial team monitor you during treatment and afterwards. Contact your advice line or tell your doctor or nurse if any side effects are bad or not getting better. 

Pembrolizumab can affect the immune system Open a glossary item. This may cause inflammation Open a glossary item and other reactions in different parts of the body. For many people the inflammation and reactions are not too bad. For some people they can cause serious side effects. 

Rarely, these side effects could be life threatening. Your doctor or nurse can explain what these side effects are, the risk of them happening and what to look out for.
If you have any of these side effects tell your doctor or nurse as soon as possible. You should tell them that you are on or have been on an immunotherapy.


The most common side effects of pembrolizumab are:

  • diarrhoea
  • a drop in the number of red blood cells causing an increased risk tiredness and breathlessness (anaemia Open a glossary item)
  • high temperatures (fever)
  • chest infections (pneumonia) 
  • shortness of breath 
  • scarring of the lungs

We have more information about:



Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Dr Kai-Keen Shiu

Supported by

Cancer Research UK & UCL Cancer Trials Centre
Merck, Sharp & Dohme
University College London (UCL)

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Last reviewed:

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