A trial of pembrolizumab and chemotherapy for small cell lung cancer (KEYNOTE-604)

Please note - this trial is no longer recruiting patients. We hope to add results when they are available.

Cancer type:

Lung cancer
Non small cell lung cancer
Secondary cancers




Phase 3

This trial is looking at pembrolizumab and chemotherapy for people with small cell lung cancer that has spread outside the lung (extensive stage).

It is for people who are going to have treatment for the first time.

More about this trial

Small cell lung cancer (SCLC) can sometimes spread to the lymph nodes outside the lung or into other parts of the body. This is extensive stage disease

Treatment for extensive stage SCLC is usually a combination of chemotherapy drugs. You have a combination of chemotherapy drugs because they tend to work better than single drugs. You often have etoposide with either:

This combination works but researchers are looking for ways to improve treatment. In this trial, they are looking at a targeted cancer drug called pembrolizumab (Keytruda). 

Pembrolizumab blocks a protein called PD-1. Doctors think it can help the immune system Open a glossary item to recognise and attack cancer cells.  

Everyone taking part in this trial has 1 of the following:

  • chemotherapy and pembrolizumab
  • chemotherapy and a dummy drug (placebo) Open a glossary item 

The main aims of this trial are to:

  • find out how well pembrolizumab and chemotherapy work together as a treatment
  • learn more about the side effects
  • learn about people’s quality of life Open a glossary item
  • find out what happens to pembrolizumab in the body (pharmacokinetics) Open a glossary item  

Who can enter

The following bullet points list 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 a newly diagnosed extensive stage SCLC (stage 4)
  • have at least 1 area of cancer that can be seen and measured on a scan
  • are willing to have a sample of tissue taken (a biopsy) Open a glossary item if there isn’t a suitable sample available. Your doctor will check for this
  • have satisfactory blood tests results
  • are well enough to carry out your normal activities, apart from heavy physical work (performance status of 0 or 1)
  • are at least 18 years old
  • are willing to use reliable contraception during treatment and for 4 months after the final dose of pembrolizumab or 6 months after the last dose of chemotherapy if there is any possibility you or your partner could become pregnant  

Who can’t take part

You cannot join this trial if any of these apply.

Cancer related

  • you have had treatment for SCLC, unless it was radiotherapy to help with symptoms (palliative radiotherapy) that you have finished more than a week ago
  • your doctor thinks you will need other cancer treatments (including radiotherapy) during this trial
  • you have had pembrolizumab before or any other similar drugs
  • your cancer has spread to your brain unless you have had treatment more than 2 weeks ago, it hasn’t got worse in the past 3 weeks and you haven’t taken steroids in the last week
  • you have had another cancer apart from carcinoma in situ Open a glossary item of the cervix and breast, basal or squamous cell skin cancer that have been successfully treated 

Medical conditions

  • you have had an experimental treatment as part of another clinical trial in the past month
  • you have had a major surgery in the past 3 weeks and you still have side effects from it
  • you have, or have had, certain lung problems such as inflammation of the lungs (pneumonitis) or interstitial lung disease
  • you have or have had an autoimmune disease Open a glossary item that needed systemic treatment in the past 2 years, apart from treatment to replace something that the body makes such as insulin or thyroxine
  • you have, or have had, problems in the brain or nerves that are caused by substances released by the cancer (neurological paraneoplastic syndrome)
  • you have problems with your bowels such as inflammation (diverticulitis), an abscess or a blockage (obstruction)
  • you are sensitive to monoclonal antibodies Open a glossary item, pembrolizumab or anything it contains
  • you have taken drugs that damp down your immune system (immunosuppressants) such as steroids in the past week unless it was a cream or inhaler
  • you have a build up of fluid in your tummy (ascites) Open a glossary item or between the sheets of tissue that cover the lung (pleural effusion) and this is causing you problems
  • you have had a live vaccine in the last month
  • you have an infection that needs treatment
  • you have HIV
  • you have hepatitis B or hepatitis C
  • you have tuberculosis
  • you have any other serious medical condition or mental health problem that the trial team thinks could affect you taking part 


  • you are pregnant or breastfeeding 

Trial design

This is an international phase 3 trial. The researchers need about 430 people worldwide and around 18 people from the UK to take part.

This trial is randomised. The people taking part are put into 1 of the following treatment groups by computer:

  • chemotherapy and pembrolizumab
  • chemotherapy and dummy drug 

Neither you nor your doctor are able to decide which group you are in. And neither you nor your doctor will know which treatment you are having. This is a double blind trial Open a glossary item


Everyone has pembrolizumab or the dummy drug as a drip into a vein every 3 weeks. Each 3 week period is called a cycle of treatment. 

You continue to have cycles of treatment of pembrolizumab or the dummy drug for as long as it is helping you and the side effects aren’t too bad. You can have treatment for up to 2 years. 

After 2 years, you may be able to continue having pembrolizumab. This is called second course phase. Your doctor can tell you more about this. 

You have a combination of 2 drugs:

  • etoposide
  • cisplatin or carboplatin (your doctor will explain which drug is best for you)

You have all drugs as a drip into a vein. You come into hospital and have etoposide on days 1, 2 and 3 of each cycle of treatment. It takes around an hour each day you have it.

You have cisplatin or carboplatin once, every 3 weeks. This continues for 12 weeks. It can take up to 2 and a half hours each time you have it.   

After you finish chemotherapy, you have a scan to find out how well the treatment has worked. Then you may have radiotherapy to the brain if your cancer got smaller or disappeared. This is called prophylactic cranial irradiation (PCI). Your doctor can tell you more about this. 

Quality of life 
Everybody taking part in this trial completes a quality of life questionnaire before starting treatment and:

  • at set times during the trial
  • at the end of treatment
  • a month after finishing treatment 

The questionnaires ask about how you have been feeling and what side affects you have had.

Blood tests 
You have extra blood tests as part of this trial. Researchers want to:

  • look for proteins called antibodies Open a glossary item that can attach to pembrolizumab
  • find out what happens to pembrolizumab in your body 

You have the extra blood tests before the start of treatment, at set times during the trial and a month after finishing treatment. 

Tissue sample
The trial team will ask to use a tissue sample of your cancer taken when you were diagnosed. You will need to have a biopsy if there isn’t a suitable sample already available. 

Researchers want to look for biomarkers Open a glossary item that can help to tell how well the treatment works.

Hospital visits

You see a doctor and have some tests before taking part. These tests might include:

During treatment, you see the trial doctor for blood tests and a physical examination every 3 weeks. 

You have a CT scan or MRI scan every 6 weeks while you are having treatment. This continues for a year. After this, you have a CT scan or MRI scan every 9 weeks. 

Your treatment continues for as long as your cancer stays the same and the side effects aren’t too bad. 

When you finish treatment, you see the trial team after a month. The trial team will then call you every 8 weeks to see how you are.   

Side effects

The trial team monitor you during the time you have treatment and you have a phone number to call them if you are worried about anything. The team will tell you about all the possible side effects before you start the trial. 

The most common side effects of pembrolizumab are:

We have more information about the side effects of pembrolizumab. And information about the side effects of:

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 Riyaz Shah 

Supported by

Merck, Sharp & Dohme

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.

Over 60,000 cancer patients enrolled on clinical trials in the UK last year.

Last reviewed:

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