Event-free survival in the NHL-B2 trial. Event-free survival of all 689 eligible patients assigned to CHOP-21 (S21; n = 178), CHOP-14 (S14; n = 172), CHOEP-21 (E21; n = 170), and CHOEP-14 (E14; n = 169). Median time of observation for all patients was 58 months.