Follicular Lymphoma (FL), Indolent B-Cell

Evidence-based treatment sequencing for follicular lymphoma, distinguishing asymptomatic low-tumor-burden disease (observation) from symptomatic disease requiring anti-CD20 chemoimmunotherapy or chemo-free R² (lenalidomide-rituximab), with anti-CD20 maintenance and EZH2-inhibitor / bispecific-antibody options at relapse.

Tumor burden and symptom assessment (GELF criteria)

1L: Anti-CD20 chemoimmunotherapy (BR / obinutuzumab-based) or R² (lenalidomide + rituximab)

For symptomatic or high-tumor-burden disease: anti-CD20 (rituximab or obinutuzumab, GALLIUM) with bendamustine or CHOP, or the chemotherapy-free R² regimen (lenalidomide + rituximab, RELEVANCE). Choice is guided by comorbidity and toxicity profile.

1L: Observation ("watch and wait")

Appropriate for asymptomatic, low-tumor-burden advanced-stage disease (does not meet GELF criteria); defers therapy without compromising overall survival, with active surveillance for progression.

maintenance: Anti-CD20 maintenance (rituximab or obinutuzumab)

Anti-CD20 maintenance following induction response prolongs progression-free survival (PRIMA).

Symptomatic progression / relapsed follicular lymphoma

2L: Alternative chemoimmunotherapy or R² (lenalidomide + rituximab)

Second-line therapy uses a non-cross-resistant anti-CD20 chemoimmunotherapy backbone or R² — rituximab + lenalidomide is category-1 in relapsed FL (AUGMENT), while obinutuzumab + bendamustine followed by obinutuzumab maintenance is preferred in rituximab-refractory disease (GADOLIN). Assess for histologic transformation at relapse.

3L+: EZH2 inhibitor (tazemetostat) or bispecific antibody (mosunetuzumab)

For multiply relapsed/refractory FL: tazemetostat (especially EZH2-mutant disease), the CD20×CD3 bispecific mosunetuzumab, or CD19-directed CAR-T. PI3K inhibitors are now rarely used following market withdrawals. Clinical-trial enrollment is encouraged.