Frontline Treatment of Follicular Lymphoma With AtezolizUmab and Obinutuzumab With and Without RadiOtherapy

This is a single-arm phase II study of obinutuzumab, atezolizumab with or without RT in treatment-naïve advanced FL. Participants will initially receive 2 cycles of induction treatment with obinutuzumab and atezolizumab. During cycle 2, participants will undergo disease assessment by PET/CT scan, results of which will determine further induction treatment. Participants in Complete Medical Response (CMR) according to Lugano criteria will receive an additional 4 cycles of induction treatment. Participants who achieve a partial response (PR), stable disease (SD) or deemed to have minor/asymptomatic progressive disease (PD) will also receive 4 further cycles of induction treatment, with the addition of involved-site RT to residual sites of disease (4Gy in 2 fractions), administered between cycle 3 and cycle 4. Participants with symptomatic PD following 2 cycles of induction treatment will not receive any further study treatment. Further treatment will be at the discretion of the treating clinician. At the end of the induction phase, disease response will again be assessed by PET/CT scan. All participants in CR, PR or SD will move into the maintenance phase of the study and will receive obinutuzumab for 24 months (up to a total of 12 doses). Participants with PD at the end of induction will cease protocol treatment and further treatment will be as per local guidelines.