A trial looking at radiotherapy to the chest after chemotherapy and rituximab for primary mediastinal large B cell lymphoma (IELSG 37)

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

Cancer type:

Blood cancers
High grade lymphoma
Non-Hodgkin lymphoma




Phase 3

This trial is trying to find the best way to treat a rare type of non Hodgkin lymphoma called primary mediastinal large B cell lymphoma. This trial is supported by Cancer Research UK.

More about this trial

Large B cell lymphoma is a type of high grade non Hodgkin lymphoma. If it starts in lymph glands Open a glossary item in the centre of your chest (the area known as the mediastinum Open a glossary item), it is called primary mediastinal large B cell lymphoma or PMBCL.

Doctors usually treat PMBCL with chemotherapy and a drug called rituximab. After this, you may also have radiotherapy to your chest to reduce the risk of the lymphoma coming back.

But having radiotherapy to your chest can increase the risk of heart problems and of getting another cancer later on. Some doctors think that leaving the radiotherapy out of treatment doesn’t make it any more likely that your lymphoma will come back.

The aim of this trial is to see if it is safe to leave radiotherapy out of the treatment plan without increasing the risk of the lymphoma coming back.

Who can enter

You may be able to enter this trial if

  • You have been diagnosed with primary mediastinal large B cell lymphoma (PMBCL) and haven’t had any other treatment yet
  • You are going to have chemotherapy and rituximab with the aim of curing your lymphoma or you have started chemotherapy and rituximab in the past 4 weeks
  • Your lymphoma cells have a protein called CD20 on their surface
  • You are at least 18 years old
  • You are willing to use reliable contraception during the trial if there is any chance you or your partner could become pregnant – women taking part must carry on using contraception for at least 3 months after treatment, men taking part must continue to use condoms for at least a year

You cannot enter this trial if you

  • Have lymphoma that has spread outside your chest
  • Have had any other cancer in the last 5 years apart from non melanoma skin cancer or carcinoma in situ of the cervix
  • Have had a heart attack in the last year or have certain other heart problems – the trial team can advise you about this
  • Are known to be HIV positive
  • Are pregnant or breastfeeding

Trial design

Everybody joining the trial has a PET-CT scan. This is either before starting chemotherapy and rituximab or within 4 weeks of starting treatment.

You can still join this study if you have already started treatment with chemotherapy and rituximab. You can enter within 4 weeks of cycle 1 of your treatment. 

After treatment for primary mediastinal large B cell lymphoma, a lot of people still have some abnormal tissue in their chest. This may be lymphoma, but often it is just scar tissue. A PET-CT can help to show the difference between active lymphoma cells and scar tissue.

When you finish your chemotherapy and rituximab treatment, you have another PET-CT scan to see how well your lymphoma has responded to treatment.

If the scan shows that there are no longer any active lymphoma cells, it is called a negative PET-CT scan. If there are still some active lymphoma cells, it is called a positive scan.

If you have a positive PET-CT scan after finishing your chemotherapy and rituximab, your doctor will decide if you need to have any further treatment. If you have a negative PET-CT scan, you are put into 1 of 2 groups by a computer. This is called randomisation. Neither you nor your doctor will be able to decide which group you are in.

People in one group have radiotherapy for 2 to 3 weeks. People in the other group have no further treatment for their lymphoma.

IELSG 37 trial diagram

Everybody has regular follow up appointments for up to 5 years. The trial team will check if

  • There are any signs of the lymphoma coming back
  • You have any long term treatment side effects

A final follow up will take place 10 years after randomisation.

Hospital visits

You see the trial team and have some tests before you start treatment. The tests include

You go to hospital regularly during chemotherapy, but no more than if you were having standard treatment Open a glossary item. The PET-CT scan you have a few weeks after finishing chemotherapy is also standard treatment.

If you have a negative PET-CT scan and you are in the group having radiotherapy, you will go to hospital every day for 2 to 3 weeks to have the treatment.

Everybody will see the trial team and have blood tests and scans every 3 months for 2 years. After that, you see the trial team and have blood tests every 6 months for the next 3 years. You may have more scans during this time.

The researchers will ask your permission to collect information from your medical notes for up to 10 years to see how you are getting on.

Side effects

It is possible that not having radiotherapy may put you at higher risk of your lymphoma coming back.  Your doctor will check for this during your follow up appointments.

If you do have radiotherapy, the possible side effects include

We have more information about the side effects of chest radiotherapy.

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 Andrew Davies

Supported by

Cancer Research UK
Experimental Cancer Medicine Centre (ECMC)
International Extranodal Lymphoma Study Group (IELSG)
NIHR Clinical Research Network: Cancer
Southampton Clinical Trials Unit
University Hospital Southampton NHS Foundation Trust

Other information

This is Cancer Research UK trial number CRUK/12/040.

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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