criteria for starting treatment. Patients receive R+chemo with the option of CVP, CHOP or bendamustine. Anatomical responders are grouped based on post-induction PET status: those who achieve a CMR (Deauville 1-3) are randomised 1:1 to R maintenance (8 weekly for 12 doses) versus no further treatment, whereas those who remain PET +ve (Deauville 4-5) are randomised 1:1 to R maintenance with or without lenalidomide. The primary endpoint is PFS with secondary endpoints including OS, toxicity, quality of life, conversion to PET negativity (PET +ve group only) and response to induction therapy. The study opened in the UK in May 2018 and Australia in February 2019 and is recruiting at the expected rate. A protocol amended is being planned to allow G as an alternative to R. In the revised design, which aims to recruit ~1000 patients from ~100 centres over 4.5 years, Rand G-treated patients will be analysed initially as a single cohort and as separate cohorts once sufficient events have accumulated. PETReA is the first trial in FL to stratify patients for separate questions based on post-induction PET status.