Follicular lymphoma (FL) is curable by involved-field radiotherapy (IFRT) in < 50% of patients with stage I to II disease. We hypothesized that adding systemic therapy to IFRT would improve long-term progression-free survival (PFS).

A multicenter randomized controlled trial enrolled patients with stage I to II low-grade FL after staging computed tomography scans and bone marrow biopsies. F-labeled fluorodeoxyglucose-positron emission tomography (PET) was not mandatory. Patients were randomly assigned to either arm A (30 Gy IFRT alone) or arm B (IFRT plus six cycles of cyclophosphamide, vincristine, and prednisolone [CVP]). From 2006, rituximab was added to arm B (R-CVP).

Between 2000 and 2012, 150 patients were enrolled, 75 per arm. In arm B, 44 patients were allocated to receive CVP and 31 were allocated to receive R-CVP. At randomization, 75% had stage I, the median age was 57 years, 52% were male, and 48% were PET staged. With a median follow-up of 9.6 years (range, 3.1 to 15.8 years), PFS was superior in arm B (hazard ratio, 0.57; 95% CI, 0.34 to 0.95; P = .033). Ten-year PFS rates were 59% (95% CI, 46% to 74%) and 41% (95% CI, 30% to 57%) for arms B and A, respectively. Patients in arm B who received R-CVP had markedly superior PFS compared with contemporaneous patients in arm A (hazard ratio, 0.26; 95% CI, 0.07 to 0.97; P = .045). Fewer involved regions ( P = .047) and PET staging ( P = .056) were associated with better PFS. Histologic transformation occurred in four and 10 patients in arms B and A, respectively ( P = .1). Ten deaths occurred in arm A versus five in arm B, but overall survival was not significantly different ( P = .40; 87% and 95% at 10 years, respectively).

Systemic therapy with R-CVP after IFRT reduced relapse outside radiation fields and significantly improved PFS. IFRT followed by immunochemotherapy is more effective than IFRT in early-stage FL.