Asymptomatic patients ( aged 18 years ) with low-tumour-burden follicular lymphoma ( grades 1 , 2 , and 3a ) were randomly assigned centrally ( 1:1:1 ) , by the minimisation approach stratified by institution , grade , stage , and age , to watchful waiting , rituximab 375 mg/m ( 2 ) weekly for 4 weeks ( rituximab induction ) , or rituximab induction followed by a maintenance schedule of 12 further infusions given at 2-monthly intervals for 2 years ( maintenance rituximab ) .