Maximum disease diameter is associated with outcomes in stage II follicular lymphoma treated with radiation therapy alone

The optimal management of stage II follicular lymphoma (FL) is unclear. Radiation therapy (RT) alone has been the gold standard treatment, but a proportion of patients relapse. We sought to characterize outcomes and prognostic factors for stage II FL treated with RT alone to identify a high-risk subgroup of patients who may benefit from treatment intensification.

This was a population-based, province-wide, retrospective study. Included patients had grade 1-3A, non-mesenteric, stage IIA or IIAE FL diagnosed between 1986 and 2016 and treated with curative-intent (≥20 Gy) RT alone.

102 patients were included. Median follow-up was 10.4 years (range, 0.3-22.3). Median age was 59 years (range, 33-86). Median greatest disease diameter was 3.6 cm (range, 1.5-11.5). Freedom from progression (FFP) was 60.3% at 5 years and 40.7% at 10 years. Overall survival (OS) was 89.2% at 5 years and 81.8% at 10 years. Greatest disease diameter of >3.6 cm was associated with inferior FFP (10-year FFP 34% vs. 47%, p = 0.013) on univariable analysis and inferior FFP (hazard ratio [HR] 1.87, p = 0.019) and inferior OS (HR 2.12, p = 0.027) on multivariable analysis (MVA). Older age was associated with inferior OS (HR 1.08, unit = 1 year, p < 0.001) on MVA.

40.7% of stage II FL patients treated with RT alone remained disease-free at 10 years. Greatest disease diameter >3.6 cm was associated with inferior FFP and OS, representing a novel prognostic indicator in this population that may help in the decision-making process on whether to complement RT with systemic therapy.