PETReA: a phase 3 trial testing whether PET scans can help make treatment decisions for people with follicular lymphoma

This trial is testing whether PET scans can help determine the need for maintenance treatment in people with previously untreated follicular lymphoma.

Purpose of trial

The aim of this trial is to find out if PET scans can be helpful in deciding whether people with follicular lymphoma need maintenance treatment after first-line treatment. It also aims to find out:

  • if rituximab maintenance can be avoided for people with a good response to first-line treatment, preventing unnecessary side effects. 
  • if adding lenalidomide to rituximab maintenance can improve outcomes for people who have residual (leftover) lymphoma after first-line treatment.

A sub-study of the PETReA trial is looking at how effective COVID-19 vaccination is for people with follicular lymphoma.


Everyone in this trial is treated with the standard first-line treatment of chemotherapy and rituximab. Your doctor can decide which of the following regimens (combinations of drugs) is most suitable for you: 

  • R-CHOP: rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone
  • BR: bendamustine, rituximab
  • R-CVP: rituximab, cyclophosphamide, vincristine, prednisolone.

You have a PET and CT scan at the end of standard treatment. The results of the scan are used to decide what treatment you need next, if any. 

If you do not respond to treatment, you leave the trial and your doctor decides what treatment you need next.

If you respond to treatment and have a negative PET scan (no active lymphoma), you are randomly assigned to one of two groups:

  • rituximab maintenance
  • no further treatment.

If you respond to treatment but have a positive PET scan (there is still active lymphoma in your body), you are randomly assigned to receive:

  • rituximab maintenance
  • rituximab and lenalidomide maintenance – this regimen (combination of drugs) is known as R2 ('R squared').

You can’t choose which treatment group you are in and neither can your doctor. You are told which treatment you are receiving and given information about it.

During rituximab maintenance, rituximab is given intravenously once every 8 weeks for up to 2 years. Some people can have rituximab subcutaneously (by injection under the skin).

Lenalidomide is taken as tablets every day for 21 days in every 28-day cycle. You continue to take this treatment for up to 2 years.

Who can enter

The trial team can advise you whether you are suitable for this trial and whether any other conditions or treatments you have or have had prevent you from entering the trial.

840 people are needed for this trial.

You may be able to enter if:

  • You have follicular lymphoma.
  • Your lymphoma needs treatment.
  • You have not previously received treatment for your follicular lymphoma.
  • You are well enough to look after yourself and are up and about at least 50% of the day even if you are unable to work.
  • Your blood and other health test results are satisfactory.
  • You are 18 or over.

You won’t be able to enter if:

  • You have had previous treatment for your lymphoma.
  • You are pregnant or breastfeeding.

Further information

More information about this trial is available at