EFS of 710 patients treated according to the NHL-B1 protocol. EFS according to the 4 treatment arms (A). A 2 × 2 factorial analysis comparing the 3-weekly regimens (CHOP-21/CHOEP-21) with the 2-weekly regimens (CHOP-14/CHOEP-14; B) and the CHOP regimens (CHOP-21/CHOP-14; C) with the etoposide-containing regimens (CHOEP-21/CHOEP-14). Effect of etoposide in stage I/II patients (D) and in stage III/IV patients (E). The median time of observation for all patients was 58 months.