Impact of age on long-term mortality and net survival benefit of radiotherapy for early-stage follicular lymphoma from the SEER database (2000-2015)

Abstract Background: The effect of age on long-term mortality and net survival benefit of radiotherapy (RT) for early-stage follicular lymphoma (FL) was not evaluated. Methods: 8,803 patients with early-stage FL in the Surveillance, Epidemiology, and End Results (SEER) database (2000-2015) were identified for this study. Primary therapy included RT (27.0%), chemotherapy (CT, 29.3%), observation (24.1%), and other/unknown treatments (19.6%). Inverse probability of treatment weighting (IPTW) was conducted to balance the treatment arms. Relative survival (RS), the standardized mortality ratio (SMR), and transformed Cox regression were used to compare survival differences between treatments.Results: The risk of dying from FL and other causes varied over time, dependent of patient age. RT had significantly higher 10-year OS (77.2%) and RS (96.1%), but lower SMR (1.77), compared with CT (65.2%; 82.6%; 2.92; P<0.001), observation (65.5%; 90.1%; 2.18; P<0.001), and other/unknown treatments (66.5%, P<0.001; 89.9%, P=0.136; 2.05, P<0.001). RT was an independent predictor of better OS and RS in multivariate analyses (P<0.001). No significant interaction between age and RT was identified for RS (Pinteraction=0.305) or OS (Pinteraction= 0.272), indicating similar survival benefits across all-ages patients.Conclusions: RT was associated with long-term OS and net survival benefits in early-stage FL.