Progression-free survival in patients treated with CHOP and R-CHOP. Median progression-free survival (PFS) was 1.2 years (95% CI: .9-1.8) in the cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) arm and 4.8 years (95% CI: 2.7-7.6) in the CHOP plus rituximab (R-CHOP) arm (P < .0001).